method-signature

问题 Why does the Objective-C compiler need to know at compile-time the signature of the methods that will be invoked on objects when it could defer that to runtime (i.e., dynamic binding)? For example, if I write [foo someMethod] , why it is necessary for the compiler to know the signature of someMethod ? 回答1: Because of calling conventions at a minimum (with ARC, there are more reasons, but calling conventions have always been a problem). You may have been told that [foo someMethod] is converted

问题 Ist it possible to cal a COM method with the signature HRESULT Foo(BSTR in, [out] BSTR * out1, [out] BSTR * out2) from VBScript? The following: Dim a; Dim b; component.Foo "something", a, b gives an error about incompatible types. I still could change the signature of the method. 回答1: Looks like output parameters are not supported; while ByRef / [in, out] parameters are, but only on VARIANT parameters. From the following KB article: INFO: Type mismatch errors when you pass parameters from an

问题 Some predefined methods contain a ParamArray in their signature. Delegates, however, cannot contain a ParamArray in their signature. Question: Assume you wish to create a delegation mechanism for a specific method which requires a ParamArray. How would you work around this constraint? EDIT: just to make clear, assume you cannot change the method signatures themselves (pre-defined methods, defined by some 3rd party, be it Microsoft or not). EDIT2: The real deal here is keeping the syntax sugar

问题 Does the method signature in a Java class/interface include its return type? Example: Does Java know the difference between those two methods: public class Foo { public int myMethod(int param) {} public char myMethod(int param) {} } Or is it maybe only the method name and parameters list that matter? 回答1: Quoting from Oracle Docs: Definition: Two of the components of a method declaration comprise the method signature —the method's name and the parameter types. Since the question was edited to

问题 I'm learning Rust and got to the chapter on trait bounds. In that chapter, they give an example with the + (plus) operator to enumerate all required traits in a where clause. What other operators are allowed on traits in Rust? I searched but I wasn't able to find any documentation about this. Does Rust support 'or' notation, brackets, negation? 回答1: 'or' notation No. Such a thing doesn't make sense to me — what would the code do if something could be A OR B ? brackets No, unless you count the

问题 I mean if it's called with $request which is not instance of sfWebRequest ,will it be fatal,or just a warning? class jobActions extends sfActions { public function executeIndex(sfWebRequest $request) { $this->jobeet_job_list = Doctrine::getTable('JobeetJob') ->createQuery('a') ->execute(); } // ... } 回答1: It will be a catchable fatal error. Here is an example: class MyObj {} function act(MyObj $o) { echo "ok\n"; } function handle_errors($errno, $str, $file, $line, $context) { echo "Caught

问题 I mean if it's called with $request which is not instance of sfWebRequest ,will it be fatal,or just a warning? class jobActions extends sfActions { public function executeIndex(sfWebRequest $request) { $this->jobeet_job_list = Doctrine::getTable('JobeetJob') ->createQuery('a') ->execute(); } // ... } 回答1: It will be a catchable fatal error. Here is an example: class MyObj {} function act(MyObj $o) { echo "ok\n"; } function handle_errors($errno, $str, $file, $line, $context) { echo "Caught

问题 Since in python 3.X the build-id range() function returns no longer a list but an iterable, some old code fails as I use range() to conveniently generate lists I need. So I try to implement my own lrange function like this: def lrange(start = 0, stop, step = 1): ret = [] while start < stop: ret.append(start) start += step return ret giving me a "non-default argument follows default argument" interpreter error. If I look at Python's range() it seems to be possible. I posted this question

问题 Is there a way to find out -- at runtime -- whether a given method is of variadic type? Something like method_getTypeEncoding() ; that won't tell me whether a method accepts variable number of arguments. Or is there maybe a trick to tell so? 回答1: Robert's comment is correct. Consider: @interface Boogity @end @implementation Boogity - (void)methodWithOneIntArg:(int)a {;} - (void)variadicMethodWithIDSentinel:(id)a, ... {;} @end Running strings on the resulting binary produces (there was also

问题 Is there a way to find out -- at runtime -- whether a given method is of variadic type? Something like method_getTypeEncoding() ; that won't tell me whether a method accepts variable number of arguments. Or is there maybe a trick to tell so? 回答1: Robert's comment is correct. Consider: @interface Boogity @end @implementation Boogity - (void)methodWithOneIntArg:(int)a {;} - (void)variadicMethodWithIDSentinel:(id)a, ... {;} @end Running strings on the resulting binary produces (there was also