PHP5 has a "magic method" __call()that can be defined on any class that is invoked when an undefined method is called -- it is roughly equivalent to Ruby's method_missing or Perl's AUTOLOAD. Is it possible to do something like this in older versions of PHP?
The most important bit that I was missing was that __call exists in PHP4, but you must enable it on a per-class basis by calling overload(), as seen in php docs here .
Unfortunately, the __call() function signatures are different between PHP4 and PHP5, and there does not seem to be a way to make an implementation that will run in both.
I recall using it, and a little bit of googling suggests that
function __call($method_name, $parameters, &$return)
{
$return_value = "You called ${method_name}!";
}
as a member function will do the job.
Related
I have a Swift application that uses a module, and I need to call a global function that is in the application from the module, is this possible?
To perhaps explain a little better, this is a test app structure:
CallbackTestApp contains a function foo(), I would like to call it from Module1 or File, will swift allow this?
edit #1
More details have been requested on what is the background of my issue, hopefully, this will not turn out to be an XY situation.
There's a tool developed by my company that process the application source* code and in some places add function call (ignore the why etc, have to be generic here.). Those function calls are exactly to foo() which then does some magic (btw, no return value and no arguments are allowed), if the application does not use modules or if modules are excluded from the processing then all is fine (Linker does not complain that the function is not defined), if there are modules then nothing works since I did not found a way to inject foo() (yet).
*Not exactly the source code, actually the bitcode is processed, the tool get the source, use llvm toolchain to generate bitcode, do some more magic and then add the call to foo() by generating it's mangled name and adding a swiftcall
Not actually sure those additional details will help.
In Swift 3.0, the automated changing of function names due to the "Omit Needless Words" rule has caused two functions in an ObjC class to be the same.
- (void)showLoader;
...and...
- (void)show __deprecated_msg("User 'showLoader'");
The problem is that these functions are within a third party Cocoa Pod (otherwise I would just delete the unnecessary 'show' function).
This results in getting the error "Ambiguous use of 'show'" when I try to invoke the function like this:
loader?.show()
Is there a way to reverse the automatic changing of function name in Swift 3.0 or to help the compiler know which function I want to invoke?
Thanks for your help!
See MartinR's answer to my similar question here: Converting to Swift 3 renamed my own Objective-C method
If you owned the code, you could use NS_SWIFT_NAME(showLoader()) after your method declaration to force the ObjC-to-Swift method conversion to be named what you want:
- (void)showLoader NS_SWIFT_NAME(showLoader());
I think it's worth mentioning even though in your case it doesn't exactly solve your problem because you don't own the code.
You can work around this by calling
loader?.perform(Selector("showLoader"))
You will see a warning from the compiler, but it will compile successfully, and things will work correctly at runtime.
I implement MyClass containing the method method() and I store the instance in $_ENV['key'] in test.php. Also in test.php the code completion works when I type $_ENV['key']->.
In test2.php I include test.php and the code completion does not work any more for $_ENV['key']->.
Does anyone know how to enable this in PhpStorm?
AFAIK type tracking for arrays works within the same file only.
You can bypass it via intermediate variable (yes, it's not a nicest solution) and small PHPDoc comment, like this:
/** #var MyClass $myVar */
$myVar = $_ENV['key'];
$myVar->
P.S.
In general, I'd suggest not using global arrays this way (or even not using global vars at all -- only very basic stuff during bootstrap, if possible). Instead (based on your code) I may suggest using some static class (as one of the alternatives) with dedicated field where you can easily give type hint (via PHPDoc) to a class field -- this way IDE will always know hat type it is. Current PHP versions (5.5 and especially 5.6) work with objects nearly as fast as with arrays, even leading in (smaller) memory consumption.
Obviously, such suggestion does not really apply if this code is not yours.
I wanted to write something like ((IStringer)object).ToString() (in C#) in Erlang. After some studying I've learnt that Elixir has something called Protocols that pretty much resembles the same thing of C# (in an inside-out manner). Then I came up with this idea/code in Erlang - which is nice enough to me like:
?stringer(my_val):to_string().
And it either returns the expected value or not_implemented atom!
But 2 questions:
1 - Why nobody use this or promote things based on stateful modules in Erlang? (OTP aside and from talking to some Erlangers they did not know that actually OTP is built around this! So really there is a need to change how Erlang is being taught and promoted. It's possible that I am confused.).
2 - Why I get this warning? That call actually can never fails.
The warning:
stringer.erl:18: Warning: invalid module and/or function name; this call will always fail
stringer.erl:19: Warning: invalid module and/or function name; this call will always fail
stringer.erl:20: Warning: invalid module and/or function name; this call will always fail
The code:
-module(stringer).
-export([to_string/1,sample/0]).
-define(stringer(V), {stringer, V}).
to_string({stringer, V}) when is_list(V) ->
to_string(V, nop);
to_string({stringer, V}) when is_atom(V) ->
to_string(V, nop);
to_string({stringer, _V}) ->
not_implemented.
to_string(V, _Nop) ->
Buffer = io_lib:format("~p",[V]),
lists:flatten(Buffer).
sample() ->
io:format("~p~n", [?stringer([1,2]):to_string()]),
io:format("~p~n", [?stringer(cute_atom):to_string()]),
io:format("~p~n", [?stringer(13):to_string()]).
And the output is:
"[1,2]"
"cute_atom"
not_implemented
I am doing this on Erlang R16 B2 (V5.10.3) 32 bit on Windows 8 64 bit.
The warning you see is an Erlang bug. If Erlang sees you are invoking a function in a literal tuple, it shows the warning. I have seen this while working with Elixir, I have silenced it in Elixir's compiler but forgot to report it to the Erlang team as a bug. Sorry.
The stateful module thing is actually avoided in Erlang by the majority of developers. They were added to support a feature called "parameterized modules", which has then since been removed, but the underlying dispatching mechanism still exists. If you search the Erlang Questions mailing list you can find plenty of discussion on the topic. Note that protocols in Elixir are not implemented like that though.
In fact, it seems your implementation does not seem to add anything compared to a regular function. For example, you could have simply written:
to_string(V) when is_list(V); is_atom(V) ->
Buffer = io_lib:format("~p",[V]),
lists:flatten(Buffer);
to_string(V) ->
not_implemented.
and called the function directly. Your implementation is simply using the classic ad-hoc polymorphism provided by Erlang at the end of the day. The limitation of this approach is that, since dispatch is hardcoded to ?stringer, the only way to extend the to_string/1 behaviour to work with a new data type is to reimplement and replace the whole stringer module.
Here is an example of an issue that helps you ponder about this: if application A defines a "protocol" named stringer, how can applications B and C extend this protocol to their own data types and all be used by application D without loss of functionality?
In very simple words, the way protocols work in Elixir is by making the stringer module an intermediate dispatch module. So the stringer module actually works like this:
to_string(V) when is_list(V) ->
string_list:to_string(V);
to_string(A) when is_atom(A) ->
string_atom:to_string(A);
%% ...
to_string(A) when is_tuple(A) ->
string_tuple:to_string(A).
and imagine that code is wrapped around something that checks if the module exists and fails accordingly if not. Of course, all of that is defined automatically for you by simply defining the protocol. There is also a mechanism (called consolidation) to compile protocols down to a fast dispatch mechanism on releases.
I'm working on a Perl module and whenever I call the skip() method I wrote in the following way:
$cursor->skip(4);
I get:
Undefined subroutine &MyModule::Cursor::skip called at t/tester.pl line 24.
(in cleanup) invalid object at t/tester.pl line 24.
When I call it like:
MyModule::Cursor::skip($cursor, 4);
Perl finds it!
Oddly, if I name "skip" anything else ("skipper", "hello"), this syntax works:
$cursor->skipper(4);
I thought maybe skip() was a "secret" reserved key word or something, but I've also got methods named sort() and next() (which I know are reserved), and those work fine.
I'd really like to name this method "skip." Does anyone know why Perl can't find it?
skip() is exported from Test::More, which you might have loaded since your executable is named t/tester.pl.
What does ref($cursor) yield you? It should be a blessed MyModule::Cursor object, but the "invalid object" error might be suggesting the object was not constructed properly.
EDIT: perldiag gives another clue: "in cleanup" signifies that a problem was encountered by the object's destructor. Assuming you don't already have a destructor in the object, create a MyModule::Cursor::DESTROY method that Data::Dumps the object to see what it looks like at this time.
A concise snippet of example code that exhibits this behaviour would be very helpful.
Without actual code, it's difficult to debug this.
Do you use MyModule::Cursor in your test code? When you replaced skip with skipper, were you calling it in exactly the same way from your test module? Are you able to use skip from a throw-away (one-liner or very short script)?
Where I'm going with this is looking for an error in your test code, rather than the module.
UPDATE: You're not doing something like declaring methods on MyModule::Cursor in two different files, are you? The error message you're getting tells me it has a blessed reference to an object of type MyModule::Cursor, so it knows about the class; but then it can't find the definition of skip. Do you happen to declare part of MyModule::Cursor in one file, and skip in another, and your test module isn't including the second file? Or do you have a syntax error somewhere around your definition of skip -- a missing semi-colon or unpaired curly brace? (But then again, why would MyModule::Cursor::skip work where $cursor->skip does not?)