As php8 allows match like :
echo match ($v) {
0 => 'Foo',
1 => 'Bar',
2 => 'Baz',
}; // Bar
I wonder if there is a way to use in match more complicated conditions, like :
if ($checkValueType == EnumType::Integer and ! isValidInteger($value) and ! empty
($default_value)) {
return $default_value;
}
if ($checkValueType == EnumType::Float and ! isValidFloat($value) and ! empty($default_value)) {
return $default_value;
}
if ($checkValueType == EnumType::Bool and ! isValidBool($value) and ! empty($default_value)) {
return $default_value;
}
return $value;
Thanks in advance!
No, you can't do that, because match is an expression, and cannot contain statements.
Structure of a match expression
$return_value = match (subject_expression) {
single_conditional_expression => return_expression,
conditional_expression1, conditional_expression2 => return_expression,
};
Related
I have a macro to generate match arms:
macro_rules! sort_by {
( $query:ident, $sort_by:expr, { $( $name:pat => $column:path,)+ } ) => {
match $sort_by.column {
$(
$name => if $sort_by.descending {
$query = $query.order_by($column.desc());
} else {
$query = $query.order_by($column.asc());
},
)+
}
}
}
and I want to call it like this:
sort_by!(query, sort_by.unwrap_or(Sort::desc("id")), {
"id" => table::id,
"customerName" => table::customer_name,
});
But I'm getting an error:
sort_by!(query, &sort_by.unwrap_or(Sort::desc("id")), {
^^^^^^^ value moved here in previous iteration of loop
So I have to call it like this:
let sort = sort_by.unwrap_or(Sort::desc("id"));
sort_by!(query, &sort, {
"id" => table::id,
"customerName" => table::customer_name,
});
What should I change to be able to use the expression directly in the macro invocation?
Using a macro is equivalent to substituting the code it expands to into its call site. This means if the macro expansion contains $sort_by multiple times, the code will evaluate the expression you pass in as $sort_by multiple times. If the expression consumes some variable, this will be invalid.
This is in contrast to how function calls work. If you pass an expression to a function, it will be evaluated before calling the function, and only the result is passed to the function.
If this is the source of your problem, you can fix it by assigning $sort_by to a local variable inside your macro expansion, and only access the local variable subsequently:
macro_rules! sort_by {
($query:ident, $sort_by:expr, { $($name:pat => $column:path,)+ }) => {
let sort_by = $sort_by;
match sort_by.column {
$(
$name => if sort_by.descending {
$query = $query.order_by($column.desc());
} else {
$query = $query.order_by($column.asc());
},
)+
}
}
}
(Note that I could not test this, since your example is incomplete.)
Intended usage:
cond! {
x > 5 => 0,
x < 3 => 1,
true => -1
}
Should expand to:
if x > 5 { 0 } else if x < 3 { 1 } else if true { -1 }
Note that it doesn't produce a catch-all else { ... } suffix.
My attempt:
macro_rules! cond(
($pred:expr => $body:expr) => {{
if $pred {$body}
}};
($pred:expr => $body:expr, $($preds:expr => $bodies:expr),+) => {{
cond! { $pred => $body } else cond! { $($preds => $bodies),+ }
}};
);
However, the compiler complains about the else keyword.
error: expected expression, found keyword `else`
--> src/main.rs:32:34
|
32 | cond! { $pred => $body } else cond! { $($preds => $bodies),+ }
| ^^^^
Macros in Rust don't perform textual substitution like the C preprocessor does. Moreover, the result of a macro is already "parsed", so you can't just append something after the macro invocation that's supposed to be part of what the macro expands to.
In your case, you can't put an else after the first cond! invocation because the compiler has already finished parsing the if expression; you need to put the if and the else together. Likewise, when you invoke cond! again after the else, you need to add braces around the call, because the sequence else if does not begin a nested if expression.
macro_rules! cond {
($pred:expr => $body:expr) => {
if $pred { $body }
};
($pred:expr => $body:expr, $($preds:expr => $bodies:expr),+) => {
if $pred { $body } else { cond! { $($preds => $bodies),+ } }
};
}
Ultimately though, this macro is pretty much useless. An if expression without an else clause always has its type inferred to be (), so unless all the branches evaluate to () (or diverge), the expanded macro will produce type mismatch errors.
My database column "status" stores "0 or 1" value but I want to display "Enable" or "disable"
Try this... This might be helpful to you.
Modify code as per your need.
[
'attribute' => 'status',
'value' => function ($model, $key, $index, $widget) {
if ($model->status == 0) {
$status = 'disable';
} elseif ($model->status == 1) {
$status = 'Enable';
} else {
$status = 'Completed';
}
return $status;
}
]
I am using a DB::CDBI class for accessing the database in our application. Our project is in object-oriented Perl.
package LT::LanguageImport;
use strict;
use warnings;
use base 'Misk5::CDBI';
__PACKAGE__->table( 'english_text_translation' );
__PACKAGE__->columns( Primary => qw/english language translation/ );
__PACKAGE__->columns( Essential => qw/english language translation/ );
__PACKAGE__->has_a( english => 'LT::EnglishLanguage' );
In one such scenario, I am supposed to check if a row in a table exists. I am using the built-in search API in a CDBI call.
sub find_translation {
my $translation_exists_r_not = $class->search(
english => $english,
language => $language,
translation => $translation
);
return;
}
$translation_exists_r_not is getting the expected values depending on the inputs given in the search. If the row exists, then the _data is updated with the row details.
$translation_exists_r_not = bless({
'_data' => [
{
'language' => 'polish',
'translation' => 'Admin',
'english' => 'admin'
}
],
'_place' => 0,
'_mapper' => [],
'_class' => 'LT::LanguageImport'
},
'Class::DBI::Iterator'
);
If the row desn't exist, then I get a return value like this.
$translation_exists_r_not = bless({
'_data' => [],
'_place' => 0,
'_mapper' => [],
'_class' => 'LT::LanguageImport'
},
'Class::DBI::Iterator'
);
I want to return the value of translation from this sub find_translation depending on the search result. I am not able to get a best condition for this.
I tried copying the _data into an array, but I'm not sure how to proceed further. As _data will be an empty arrayref and another condition it will have a hashref inside the arrayref.
my #Arr = $translation_exists_r_not->{'_data'};
CDBI's search method will return an iterator, because there may be multiple rows returned depending on your criteria.
If you know there can be only one row that matches your criteria, you want to use the retrieve method, i.e.:
if (my $translation_exists_r_not = $class->retrieve(
english => $english,
language => $language,
translation => $translation
)){
return [$translation_exists_r_not->translation,
'Misk5::TranslationAlreadyExists']
}
else {
return [ '', undef ]
}
And if multiple rows can be returned from your search, and you're only interested in the truthiness, then again, don't be rummaging around inside the CDBI::Iterator, but use its methods:
my $translation_exists_r_not = $class->search(
english => $english,
language => $language,
translation => $translation
); # returns an iterator
if ($translation_exists_r_not){
my $first = $translation_exists_r_not->first;
return [ $first->translation, 'Misk5::TranslationAlreadyExists' ]
}
Have a look at perldoc Class::DBI and perldoc Class::DBI::Iterator. CDBI has excellent documentation.
I think I got the solution. Thanks to whoever has tried to solve it.
my #req_array = %$translation_exists_r_not->{_data};
my $length_of_data = '9';
foreach my $elem (#req_array) {
$length_of_data = #{$elem};
}
Now check the length of the array.
if ($length_of_data == 0) {
$error = '';
$result = [undef, $error];
}
Now check if it is one.
if ($length_of_data == 1) {
my #result_array = #{%$translation_exists_r_not->{_data}};
my $translation = $result_array[0]{'translation'};
$error = 'Misk5::TranslationAlreadyExists';
$result = [$translation, $error];
}
return #$result;
I decided to use eXist as a database for an application that I am writing in Perl and
I am experimenting with it. The problem is that I have stored a .xml document with the following structure
<foo-bar00>
<perfdata datum="GigabitEthernet3_0_18">
<cli cmd="whatsup" detail="GigabitEthernet3/0/18" find="" given="">
<input_rate>3</input_rate>
<output_rate>3</output_rate>
</cli>
</perfdata>
<timeline>2011-5-23T11:15:33</timeline>
</foo-bar00>
and it is located in the "/db/LAB/foo-bar00/2011/5/23/11_15_33.xml" collection.
I can successfully query it, like
my $xquery = 'doc("/db/LAB/foo-bar00/2011/5/23/11_15_33.xml")' ;
or $xquery can be equal to
= doc("/db/LAB/foo-bar00/2011/5/23/11_15_33.xml")/foo-bar00/perfdata/cli/data(output_rate)
or
= doc("/db/LAB/foo-bar00/2011/5/23/11_15_33.xml")/foo-bar00/data(timeline)
my ($rc1, $set) = $eXist->executeQuery($xquery) ;
my ($rc2, $count) = $eXist->numberOfResults($set) ;
my ($rc3, #data) = $eXist->retrieveResults($set) ;
$eXist->releaseResultSet($set) ;
print Dumper(#data) ;
And the result is :
$VAR1 = {
'hitCount' => 1,
'foo-bar00' => {
'perfdata' => {
'cli' => {
'given' => '',
'detail' => 'GigabitEthernet3/0/18',
'input_rate' => '3',
'cmd' => 'whatsup',
'output_rate' => '3',
'find' => ''
},
'datum' => 'GigabitEthernet3_0_18'
},
'timeline' => '2011-5-23T11:15:33'
}
};
---> Given that I know the xml document that I want to retrieve info from.
---> Given that I want to retrieve the timeline information.
When I am writing :
my $db_xml_doc = "/db/LAB/foo-bar00/2011/5/23/11_15_33.xml" ;
my ($db_rc, $db_datum) = $eXist->queryXPath("/foo-bar00/timeline", $db_xml_doc, "") ;
print Dumper($db_datum) ;
The result is :
$VAR1 = {
'hash' => 1717362942,
'id' => 3,
'results' => [
{
'node_id' => '1.2',
'document' => '/db/LAB/foo-bar00/2011/5/23/11_15_33.xml'
}
]
};
The question is : How can I retrieve the "timeline" info ? Seems that the "node_id" variable (=1.2) can points to the "timeline" info, but how can I use it ?
Thank you.
use XML::LibXML qw( );
my $parser = XML::LibXML->new();
my $doc = $parser->parse_file('a.xml');
my $root = $doc->documentElement();
my ($timeline) = $root->findnodes('timeline');
if ($timeline) {
print("Exists: ", $timeline->textContent(), "\n");
}
or
my ($timeline) = $root->findnodes('timeline/text()');
if ($timeline) {
print("Exists: ", $timeline->getValue(), "\n");
}
I could have used /foo-bar00/timeline instead of timeline, but I didn't see the need.
Don't know if you're still interested, but you could either retrieve the doc as DOM and apply an xquery to the DOM, or, probably better, only pull out the info you want in the query that you submit to the server.
Something like this:
for $p in doc("/db/LAB/foo-bar00/2011/5/23/11_15_33.xml")//output_rate
return
<vlaue>$p</value>