I have the following code in our webapp written using Mojolicious, and it doesn't work as expected: the bridge handler doesn't get the correct stash data derived from routes (gets undef), so the rest of code fails, however, debug output of $self->stash('city') in any of route handlers is as expected.
...
# Router.
my $r = $self->routes->bridge->to('Main#common');
$r->route('/')->to('Main#index')->name('start');
$r->route('/:region/:city/category/:id')->to('Main#list_category')->name('list_category');
$r->route('/:region/:city/part/:id/:name')->to('Main#show_part')->name('show_part');
...
# Controller.
sub common
{
my $self=shift;
my $db=$self->db;
my $city=$self->stash('city');
my $region=$self->db->selectrow_hashref('select * from region where LOWER(translit)=? ORDER BY region_id LIMIT 1',undef,$city);
say "City=$city.";
if(!$region)
{
$region={};
}
$self->stash(region=>$region);
return 1;
}
...
I think it's correct behavior.
Look at this code.
Placeholder is added when the appropriate route is taken to the processing, i.e., step by step.
Really, look at you routes.
my $r = $self->routes->bridge->to('Main#common');
$r->route('/')->to('Main#index')->name('start');
$r->route('/:region/:city/category/:id')->to('Main#list_category')->name('list_category');
$r->route('/:region/:city/part/:id/:name')->to('Main#show_part')->name('show_part');
I can't understand what behavior you expect when go to route /.
Sub common will be invoked in this case. There are no value for placeholder city!
So, correct solution for your routes must look like this:
my $r = $self->routes;
$r->route('/')->to('Main#index')->name('start');
my $r_city = $r->bridge('/:region/:city/')->to('Main#common');
$r_city->route('/category/:id')->to('Main#list_category')->name('list_category');
$r_city->route('/part/:id/:name')->to('Main#show_part')->name('show_part');
By the way,
starting from Mojolicious version 6.0 bridge was deprecated to favor under. So, you need to replace bridge on under.
But, if you very-very want to have value of placeholder city in common function, you may look at this two line.
You need to write this BAD code in common sub:
sub common {
my $self = shift;
my $stack = $self->match->stack;
warn $self->dumper($stack);
...
}
Print $stack and you understand how to get value of placeholder city.
Related
I am trying to filter a liststore using the GTK2::TreeModelFilter. I can't seem to find an example online that uses perl and I am getting syntax errors. Can someone help me with the syntax below? The $unfiltered_store is a liststore.
$filtered_store = Gtk2::TreeModeFilter->new($unfiltered_store);
$filtered_store->set_visible_func(get_end_products, $unfiltered_store);
$combobox = Gtk2::ComboBoxEntry->new($filtered_store,1);
Then somewhere below:
sub get_end_products {
my ($a, $b) = #_;
warn(Dumper(\$a));
warn(Dumper(\$b));
return true; # Return all rows for now
}
Ultimately what I want to do is look at column 14 of the listore ($unfiltered_store) and if it is a certain value, then it filtered into the $filtered_store.
Can someone help me with the syntax on this? I checked a bunch of sites, but they're in other languages and using different syntax (like 'new_filter' -- doesn't exist with Perl GTK).
This is the most elegant solution to a fix I need to make and I would prefer to learn how to use this rather than using a brute force method of pulling and saving the filtered data.
The set_visible_func method of the filtered store should get a sub reference as the first argument, but you are not passing a sub reference here:
$filtered_store->set_visible_func(get_end_products, $unfiltered_store);
This will instead call the sub routine get_end_products and then pass on its return value (which is not a sub reference). To fix it add the reference operator \& in front of the sub name:
$filtered_store->set_visible_func(\&get_end_products, $unfiltered_store);
Regarding your other question in the comments:
According to the documentation the user data parameter is passed as the third parameter to get_end_products, so you should define it like this:
sub get_end_products {
my ($model, $iter, $user_data) = #_;
# Do something with $user_data
return TRUE;
}
If for some reason $unfiltered_store is not passed on to get_end_products, you can try pass it using an anonymous sub instead, like this:
$filtered_store->set_visible_func(
sub { get_end_products( $unfiltered_store) });
Assume the following code:
package Thing;
sub new {
my $this=shift;
bless {#_},$this;
}
sub name {
my $this=shift;
if (#_) {
$this->{_name}=shift;
}
return $this->{_name};
}
Now assume we've instantiated an object thusly:
my $o=Thing->new();
$o->name('Harold');
Good enough. We could also instantiate the same thing more quickly with either of the following:
my $o=Thing->new(_name=>'Harold'); # poor form
my $o=Thing->new()->name('Harold');
To be sure, I allowed attributes to be passed in the constructor to allow "friendly" classes to create objects more completely. It could also allow for a clone-type operator with the following code:
my $o=Thing->new(%$otherthing); # will clone attrs if not deeper than 1 level
This is all well and good. I understand the need for hiding attributes behind methods to allow for validation, etc.
$o->name; # returns 'Harold'
$o->name('Fred'); # sets name to 'Fred' and returns 'Fred'
But what this doesn't allow is easy manipulation of the attribute based on itself, such as:
$o->{_name}=~s/old/ry/; # name is now 'Harry', but this "exposes" the attribute
One alternative is to do the following:
# Cumbersome, not syntactically sweet
my $n=$o->name;
$n=~s/old/ry/;
$o->name($n);
Another potential is the following method:
sub Name :lvalue { # note the capital 'N', not the same as name
my $this=shift;
return $this->{_name};
}
Now I can do the following:
$o->Name=~s/old/ry/;
So my question is this... is the above "kosher"? Or is it bad form to expose the attribute that way? I mean, doing that takes away any validation that might be found in the 'name' method. For example, if the 'name' method enforced a capital first letter and lowercase letters thereafter, the 'Name' (capital 'N') bypasses that and forces the user of the class to police herself in the use of it.
So, if the 'Name' lvalue method isn't exactly "kosher" are there any established ways to do such things?
I have considered (but get dizzy considering) things like tied scalars as attributes. To be sure, it may be the way to go.
Also, are there perhaps overloads that may help?
Or should I create replacement methods in the vein of (if it would even work):
sub replace_name {
my $this=shift;
my $repl=shift;
my $new=shift;
$this->{_name}=~s/$repl/$new/;
}
...
$o->replace_name(qr/old/,'ry');
Thanks in advance... and note, I am not very experienced in Perl's brand of OOP, even though I am fairly well-versed in OOP itself.
Additional info:
I guess I could get really creative with my interface... here's an idea I tinkered with, but I guess it shows that there really are no bounds:
sub name {
my $this=shift;
if (#_) {
my $first=shift;
if (ref($first) eq 'Regexp') {
my $second=shift;
$this->{_name}=~s/$first/$second/;
}
else {
$this->{_name}=$first;
}
}
return $this->{_name};
}
Now, I can either set the name attribute with
$o->name('Fred');
or I can manipulate it with
$o->name(qr/old/,'ry'); # name is now Harry
This still doesn't allow stuff like $o->name.=' Jr.'; but that's not too tough to add. Heck, I could allow calllback functions to be passed in, couldn't I?
Your first code example is abolutely fine. This is a standard method to write accessors. Of course this can get ugly when doing a substitution, the best solution might be:
$o->name($o->name =~ s/old/ry/r);
The /r flag returns the result of the substitution. Equivalently:
$o->name(do { (my $t = $o->name) =~ s/old/ry/; $t });
Well yes, this 2nd solution is admittedly ugly. But I am assuming that accessing the fields is a more common operation than setting them.
Depending on your personal style preferences, you could have two different methods for getting and setting, e.g. name and set_name. (I do not think get_ prefixes are a good idea – 4 unneccessary characters).
If substituting parts of the name is a central aspect of your class, then encapsulating this in a special substitute_name method sounds like a good idea. Otherwise this is just unneccessary ballast, and a bad tradeoff for avoiding occasional syntactic pain.
I do not advise you to use lvalue methods, as these are experimental.
I would rather not see (and debug) some “clever” code that returns tied scalars. This would work, but feels a bit too fragile for me to be comfortable with such solutions.
Operator overloading does not help with writing accessors. Especially assignment cannot be overloaded in Perl.
Writing accessors is boring, especially when they do no validation. There are modules that can handle autogeneration for us, e.g. Class::Accessor. This adds generic accessors get and set to your class, plus specific accessors as requested. E.g.
package Thing;
use Class::Accessor 'antlers'; # use the Moose-ish syntax
has name => (is => 'rw'); # declare a read-write attribute
# new is autogenerated. Achtung: this takes a hashref
Then:
Thing->new({ name => 'Harold'});
# or
Thing->new->name('Harold');
# or any of the other permutations.
If you want a modern object system for Perl, there is a row of compatible implementations. The most feature-rich of these is Moose, and allows you to add validation, type constraints, default values, etc. to your attributes. E.g.
package Thing;
use Moose; # this is now a Moose class
has first_name => (
is => 'rw',
isa => 'Str',
required => 1, # must be given in constructor
trigger => \&_update_name, # run this sub after attribute is set
);
has last_name => (
is => 'rw',
isa => 'Str',
required => 1, # must be given in constructor
trigger => \&_update_name,
);
has name => (
is => 'ro', # readonly
writer => '_set_name', # but private setter
);
sub _update_name {
my $self = shift;
$self->_set_name(join ' ', $self->first_name, $self->last_name);
}
# accessors are normal Moose methods, which we can modify
before first_name => sub {
my $self = shift;
if (#_ and $_[0] !~ /^\pU/) {
Carp::croak "First name must begin with uppercase letter";
}
};
The purpose of class interface is to prevent users from directly manipulating your data. What you want to do is cool, but not a good idea.
In fact, I design my classes, so even the class itself doesn't know it's own structure:
package Thingy;
sub new {
my $class = shift;
my $name = shift;
my $self = {};
bless, $self, $class;
$self->name($name);
return $self;
}
sub name {
my $self = shift;
my $name = shift;
my $attribute = "GLUNKENSPEC";
if ( defined $name ) {
$self->{$attribute} = $name;
}
return $self->{$attribute};
}
You can see by my new constructor that I could pass it a name for my Thingy. However, my constructor doesn't know how I store my name. Instead, it merely uses my name method to set the name. As you can see by my name method, it stores the name in an unusual way, but my constructor doesn't need to know or care.
If you want to manipulate the name, you have to work at it (as you showed):
my $name = $thingy->name;
$name =~ s/old/ry/;
$thingy->name( $name );
In fact, a lot of Perl developers use inside out classes just to prevent this direct object manipulation.
What if you want to be able to directly manipulate a class by passing in a regular expression? You have to write a method to do this:
sub mod_name {
my $self = shift;
my $pattern = shift;
my $replacement = shift;
if ( not defined $replacement ) {
croak qq(Some basic error checking: Need pattern and replacement string);
}
my $name = $self->name; # Using my name method for my class
if ( not defined $name ) {
croak qq(Cannot modify name: Name is not yet set.);
}
$name = s/$pattern/$replacement/;
return $self->name($name);
}
Now, the developer can do this:
my $thingy->new( "Harold" );
$thingy->mod_name( "old", "new" );
say $thingy->name; # Says "Harry"
Whatever time or effort you save by allowing for direct object manipulation is offset by the magnitude of extra effort it will take to maintain your program. Most methods don't take more than a few minutes to create. If I suddenly got an hankering to manipulate my object in a new and surprising way, it's easy enough to create a new method to do this.
1. No. I don't actually use random nonsense words to protect my class. This is purely for demo purposes to show that even my constructor doesn't have to know how methods actually store their data.
I understand the need for hiding attributes behind methods to allow for validation, etc.
Validation is not the only reason, although it is the only one you refer to. I mention this because another is that encapsulation like this leaves the implementation open. For example, if you have a class which needs to have a string "name" which can be get and set, you could just expose a member, name. However, if you instead use get()/set() subroutines, how "name" is stored and represented internally doesn't matter.
That can be very significant if you write bunches of code with uses the class and then suddenly realize that although the user may be accessing "name" as a string, it would be much better stored some other way (for whatever reason). If the user was accessing the string directly, as a member field, you now either have to compensate for this by including code that will change name when the real whatever is changed and...but wait, how can you then compensate for the client code that changed name...
You can't. You're stuck. You now have to go back and change all the code that uses the class -- if you can. I'm sure anyone who has done enough OOP has run into this situation in one form or another.
No doubt you've read all this before, but I'm bringing it up again because there are a few points (perhaps I've misunderstood you) where you seem to outline strategies for changing "name" based on your knowledge of the implementation, and not what was intended to be the API. That is very tempting in perl because of course there is no access control -- everything is essential public -- but it is still a very very bad practice for the reason just described.
That doesn't mean, of course, that you can't simply commit to exposing "name" as a string. That's a decision and it won't be the same in all cases. However, in this particular case, if what you are particularly concerned with is a simple way to transform "name", IMO you might as well stick with a get/set method. This:
# Cumbersome, not syntactically sweet
Maybe true (although someone else might say it is simple and straightforward), but your primary concern should not be syntactic sweetness, and neither should speed of execution. They can be concerns, but your primary concern has to be design, because no matter how sweet and fast your stuff is, if it is badly designed, it will all come down around you in time.
Remember, "Premature optimization is the root of all evil" (Knuth).
So my question is this... is the above "kosher"? Or is it bad form to expose the attribute that way?
It boils down to: Will this continue to work if the internals change? If the answer is yes, you can do many other things including but not limited to validation.)
The answer is yes. This can be done by having the method return a magical value.
{
package Lvalue;
sub TIESCALAR { my $class = shift; bless({ #_ }, $class) }
sub FETCH { my $self = shift; my $m = $self->{getter}; $self->{obj}->$m(#_) }
sub STORE { my $self = shift; my $m = $self->{setter}; $self->{obj}->$m(#_) }
}
sub new { my $class = shift; bless({}, $class) }
sub get_name {
my ($self) = #_;
return $self->{_name};
}
sub set_name {
my ($self, $val) = #_;
die "Invalid name" if !length($val);
$self->{_name} = $val;
}
sub name :lvalue {
my ($self) = #_;
tie my $rv, 'Lvalue', obj=>$self, getter=>'get_name', setter=>'set_name';
return $rv;
}
my $o = __PACKAGE__->new();
$o->name = 'abc';
print $o->name, "\n"; # abc
$o->name = ''; # Invalid name
I am having troubles mocking a subroutine in another module than where I am running the tests.
I have my tests in a file called ParserTests.pl. I am trying to test a subroutine (parse) in a module LogParser.pm
sub parse {
my ($self) = #_;
my $rr = $self->getRR;
while(1) {
my $result = $self->parseCommitSet();
if ($result eq 2) {
last;
}
my $printStatus = $self->printOut($result);
if (!$printStatus) {
say "Problem occurred with writing to output";
return 0;
}
$self->setRR(ReportRecord->new());
}
return 1;
}
I am trying to mock printOut so that it always returns true. What I am trying to do is this:
#! /usr/bin/perl
use v5.10.0;
use strict;
use warnings;
use Test::More 'no_plan';
use Test::MockObject;
use LogParser;
{other tests…}
my $mock = Test::MockObject->new();
$mock->set_true('LogParser::printOut');
my $test100FH = getTestFH($test100SetsNoPrev);
$logParser = LogParser->new($test100FH);
is($logParser->parse, 1, "im ok?");
close $test100FH;
But this test is failing. Can you tell me why and point me in the right path to get it working correctly for when I test parse()? I read up on a bunch of documentation but something like this is still a bit unclear.
The error is
Can't use an undefined value as a symbol reference at /Users/achu/Documents/workspace/Perl_Script/LogParser.pm line 241, <$fh> line 8371.
# Looks like your test exited with 25 just after 91.
That line (line 241) is inside the printOut subroutine though which means that it's not mocking that subroutine like I wanted it to. What am I doing wrong?
Test::MockModule is probably better suited to this;
my $module = Test::MockModule->new('LogParser');
$module->mock( printOut => sub { return 1 } );
This will cause LogParser to use your mocked version until $module goes out of scope.
Test::MockObject does not quite do what you want. It is good for supplying a minimally-implemented stub. But for making an instance of the class under test and selectively overriding its methods, you want Test::MockObject::Extends.
TMOE takes an instance and then lets you change what some of its methods do. In your example, you can use it to write the test thus:
use Test::MockObject::Extends;
my $test100FH = getTestFH($test100SetsNoPrev);
$logParser = Test::MockObject::Extends->new(
LogParser->new($test100FH);
);
$logParser->set_true('printOut');
is($logParser->parse, 1, "im ok?");
close $test100FH;
You didn't provide the error message, but what you've defined is an object called $mock that contains a 'printout' method. But you're calling printout() on $logparser.
The point of MockObject is to create a very bare object, with a few methods so you can test other pieces of code in a algorithm that relies on an external object. For example, you could mock a database handle so that calling $dbh->fetchStuff() always returns on static row, so that you can test the code that consumes the row.
So without more context, I can't tell the possibilities for just creating a stub for printOut() so that parse knows about it.
That being said, I also don't understand the desire to have a test for the return value of the stubbed method.
Please read the documentation for Test::MockObject and try to understand how it works.
You are doing only the first half of what is actually required: You are creating a mock object. But this will not magically end up in your LogParser.
What Test::MockObject gives you is an object that behaves just like the object you want to mock. Of course, somebody or something still has to use that object. And this will have to be the code you are trying to test.
Greetings,
I'm new to Catalyst and I am attempting to implement some dispatch logic.
My database has a table of items, each with a unique url_part field, and every item has a parent in the same table, making a tree structure. If baz is a child of bar which is a child of foo which is a child of the root, I want the URL /foo/bar/baz to map to this object. The tree can be any depth, and users will need to be able to access any node whether branch or leaf.
I have been looking through the documentation for Chained dispatchers, but I'm not sure if this can do what I want. It seems like each step in a chained dispatcher must have a defined name for the PathPart attribute, but I want my URLs to be determined solely by the database structure.
Is this easy to implement with the existing Catalyst dispatcher, or will I need to write my own dispatch class?
Thanks! :)
ETA:
I figured out that I can use an empty Args attribute to catch an arbitrary number of arguments. The following seems to successfully catch every request under the root:
sub default :Path :Args() {
my ( $self, $c ) = #_;
my $path = $c->request->path;
$c->response->status( 200 );
$c->response->body( "Your path is $path" );
}
From there I can manually parse the path and get what I need, however, I don't know if this is the best way to accomplish what I'm after.
It depends on the structure of your data, which I'm not completely clear on from your question.
If there is a fixed number of levels (or at least a limited range of numbers of levels) with each level corresponding to a specific sort of thing, then Chained can do what you want -- it's valid (and downright common) to have a chained action with :CaptureArgs(1) PathPart('') which will create a /*/ segment in the path -- that is, it gobbles up one segment of the path without requiring any particular fixed string to show up.
If there's not any such thing -- e.g. you're chasing an unlimited number of levels down an arbitrary tree, then a variadic :Args action is probably exactly what you want, and there's nothing dirty in using it. But you don't need to be decoding $c->req->path yourself -- you can get the left-over path segments from $c->req->args, or simply do my ($self, $c, #args) = #_; in your action.
You can write a new DispatchType, but it's just not likely to be worth the payoff.
After playing around with various options, I believe I've arrived at an acceptable solution. Unfortunately, I couldn't get a recursive dispatch going with :Chained (Catalyst complains if you try to chain a handler to itself. That's no fun.)
So I ended up using a single handler with a large CaptureArgs, like this:
sub default : CaptureArgs(10) PathInfo('') {
my ( $self, $c, #args ) = #_;
foreach my $i( 0 .. $#args ) {
my $sub_path = join '/', #args[ 0 .. $i ];
if ( my $ent = $self->_lookup_entity( $c, $sub_path ) ) {
push #{ $c->stash->{ent_chain} }, $ent;
next;
}
$c->detach( 'error_not_found' );
}
my $chain = join "\n", map { $_->entity_id } #{ $c->stash->{ent_chain} };
$c->response->content_type( 'text/plain' );
$c->response->body( $chain );
}
If I do a GET on /foo/bar/baz I get
foo
foo/bar
foo/bar/baz
which is what I want. If any part of the URL doesn't correspond to an object in the DB, I get a 404.
This works fine for my application, which will never have things ten-levels deep, but I wish I could find a more general solution that could support an arbitrary-depth tree.
I simply hate how CGI::Application's accessor for the CGI object is called query.
I would like my instance classes to be able to use an accessor named cgi to get the CGI object associated with the current instance of my CGI::Application subclass.
Here is a self-contained example of what I am doing:
package My::Hello;
sub hello {
my $self =shift;
print "Hello #_\n";
}
package My::Merhaba;
use base 'My::Hello';
sub merhaba {
goto sub { shift->hello(#_) };
}
package main;
My::Merhaba->merhaba('StackOverflow');
This is working as I think it should and I cannot see any problems (say, if I wanted to inherit from My::Merhaba: Subclasses need not know anything about merhaba).
Would it have been better/more correct to write
sub merhaba {
my $self = shift;
return $self->hello(#_);
}
What are the advantages/disadvantages of using goto &NAME for the purpose of aliasing a method name? Is there a better way?
Note: If you have an urge to respond with goto is evil don't do it because this use of Perl's goto is different than what you have in mind.
Your approach with goto is the right one, because it will ensure that caller / wantarray and the like keep working properly.
I would setup the new method like this:
sub merhaba {
if (my $method = eval {$_[0]->can('hello')}) {
goto &$method
} else {
# error code here
}
}
Or if you don't want to use inheritance, you can add the new method to the existing package from your calling code:
*My::Hello::merhaba = \&My::Hello::hello;
# or you can use = My::Hello->can('hello');
then you can call:
My::Hello->merhaba('StackOverflow');
and get the desired result.
Either way would work, the inheritance route is more maintainable, but adding the method to the existing package would result in faster method calls.
Edit:
As pointed out in the comments, there are a few cases were the glob assignment will run afoul with inheritance, so if in doubt, use the first method (creating a new method in a sub package).
Michael Carman suggested combining both techniques into a self redefining function:
sub merhaba {
if (my $method = eval { $_[0]->can('hello') }) {
no warnings 'redefine';
*merhaba = $method;
goto &merhaba;
}
die "Can't make 'merhaba' an alias for 'hello'";
}
You can alias the subroutines by manipulating the symbol table:
*My::Merhaba::merhaba = \&My::Hello::hello;
Some examples can be found here.
I'm not sure what the right way is, but Adam Kennedy uses your second method (i.e. without goto) in Method::Alias (click here to go directly to the source code).
This is sort of a combination of Quick-n-Dirty with a modicum of indirection using UNIVERSAL::can.
package My::Merhaba;
use base 'My::Hello';
# ...
*merhaba = __PACKAGE__->can( 'hello' );
And you'll have a sub called "merhaba" in this package that aliases My::Hello::hello. You are simply saying that whatever this package would otherwise do under the name hello it can do under the name merhaba.
However, this is insufficient in the possibility that some code decorator might change the sub that *My::Hello::hello{CODE} points to. In that case, Method::Alias might be the appropriate way to specify a method, as molecules suggests.
However, if it is a rather well-controlled library where you control both the parent and child categories, then the method above is slimmmer.