I don't think this is possible, but is there a way to validate the arguments a callback accepts. For example someone passes me callback "mycallback", I want to assert it accepts an argument String.
public function addHandler(handler : Function) : void{
//pseudo code
Assert.functionAcceptsArguments(handler, String);
}
Cheers
No you can't. If you had some object as argument you could use describeType which returns information about methods too. But Function is just a function with no information about arguments.
To be sure that you get right method signature you could pass typed objects not Functions. For example
interface Bla {
funciton invoke(value:String):void;
}
function addHandler(handler:Bla):void {}
Related
I'm still ramping up in lua, and I am not quite familiar with this syntax. What is happening when you pass in a function as a parameter like below?
Comm.setRouting(function(url)
for i = 1,4 do
local portIndex = "Path"..i
if url:match(portConfig[portIndex]) ~= nil then
return Comm.slots()[1], Comm.groups()[i]
end
end
end)
The other answers are correct, but it might help you if you wrote your own function that calls another function:
function CallAFunction(func_to_call)
func_to_call()
end
You could pass a named function (an anonymous function assigned to a variable) or an anonymous function written on the fly.
function SayHello()
print("Hello!")
end
--[[
^This is equivalent to:
SayHello = function()
print("Hello!")
end
]]--
CallAFunction(SayHello)
CallAFunction(function()
print("Goodbye!")
end)
output:
Hello!
Goodbye!
and this can be done with parameters
function CallAFunction(func)
func("Bonjour")
end
CallAFunction(function(parameter)
print(parameter)
end)
Here, func is the anonymous function, which accepts 1 parameter parameter.
When you call func("Bonjour") you are passing Bonjour as parameter, like a normal function call.
Here you're passing an argument to setRouting that is an "anonymous function"
Functions are first-class values in Lua and can be stored in local variables, global variables and table fields. Here the function is being passed anonymously on the call stack to the setRouting function.
setRouting would be called a "higher-order function" because it accepts a function as its input.
The following page has some more information about functions in Lua:
https://www.lua.org/pil/6.html
A couple of things are happening in this example:
You're passing a function as a parameter. The callee (e.g. setRouting()) can invoke that function. This is often referred to as a callback function.
You're defining the function itself, on-the-fly. This is an example of an "anonymous function", or a lambda function.
In the same way we can have
nullableClassInstance?.method(blah)
Is there a way to do
nullableFunctionInstance?(blah)
In other words, is there an operator that checks whether a function instance is not null, if so, invoke the function all in one line?
Using the call method, you can achieve what you want with:
nullableFunctionInstance?.call(blah)
There's also the apply method if you want to pass arguments.
If you have a Function Object , you can use the call method and send all the parameters to that which works exactly as calling the function. Here , you can use the null aware member access operator.
void myFun(int a , int b){...}
var myVar = myFun ;
call
The function myVar will only get called if its not null as shown below.
myVar?.call( arg1 , arg2 );
apply
If your function is dynamic or you wish to control which function is being called at run time , you can use the apply static method of Function like so :
Function.apply(myVar , [arg1 , arg2]);
apply takes the function and a List of parameters that will be sent to the function.
Read more about call and apply :
I made a custom component which basically wraps a d3 line chart. Now I want to be able to register a callback for clicks on the lines in the chart.
I gave the component a #NgCallback parameter, which I then send events to:
class NetworkSummaryComponent implements NgShadowRootAware {
#NgCallback('callback')
Function callback;
void onShadowRoot(ShadowRoot shadowRoot) {
...
chart.callMethod('listen', ['line-click', (ev) {
var name = ev.callMethod('getLineName');
print(name);
callback({'name': name});
}]);
}
}
When using the component, I specify a function of my controller as callback:
<network-summary
...
callback="ctrl.lineClicked">
</network-summary>
However, that function is never actually called, put I know the callback arrives from the JS side because the print in the first snippet is executed.
If I instead specify the attribute as callback="ctrl.lineClicked()" I get a strange exception:
Closure call with mismatched arguments: function 'call'
I could not find any official documentation on how to properly do callbacks, so I'm not exactly sure what I'm doing wrong.. Any ideas?
It turns out that I had to explicitly name the expected arguments in the attributes:
<network-summary
...
callback="ctrl.lineClicked(name)">
</network-summary>
Hope this is useful to the next person having this problem.
I'm adapting the Clang tool-template (as described here) to search for a particular method call in my code. In order to later rewrite that call, I would like to get the type of the parameters the method was called with, as well as the type of the object the method was called on.
I managed to find a matcher that calls back the following:
class AddListenerPrinter : public MatchFinder::MatchCallback
{
public :
virtual void run(const MatchFinder::MatchResult &Result) {
if (const auto *FS = Result.Nodes.getNodeAs<clang::MemberExpr>("ListeningBound"))
{
FS->dump();
}
}
};
which prints out:
MemberExpr 0x7fb05b07b948 '<bound member function type>' .addListener 0x7fb05b077670
`-MemberExpr 0x7fb05b07b918 'class MyCore' lvalue ->mCore 0x7fb05b078e30
`-CXXThisExpr 0x7fb05b07b900 'class MyComponent *' this
Now I can't find any way to retrieve the type of the object the method was called on (here class MyCore) or the type of the method argument (here class MyComponent).
How can I do this?
I found the answer by browsing the code of the existing matchers.
Using matcher = memberCallExpr( callee(methodDecl(hasName("addListener"))) )
I was able to retrieve a CXXMemberCallExpr node. Then getting the type of the object the method was called on:
// FS is the CXXMemberCallExpr
// Prints out the type of x in x.method()
llvm::outs() << FS->getRecordDecl()->getName();
and the method parameters are accessible through FS->getArg(n).
Bottom line is: Find the CXX object that contains what you're looking for first (e.g. which class has methods to access function arguments?), then find the matcher that will return the same type of object in ASTMatchers.h.
Hoping this can help anybody else with the same problem.
I'm trying to verify that a function on a mock object is NOT called at all with ANY parameters.
The function on the object I'm mocking is...
- (void)registerUserWithUsername:(NSString*)username password:(NSString*)password;
I'd like to verify that the function is NOT called if the username is blank.
i.e.
[mockService registerUserWithUsername:#"" password:#"Password"];
[verify(mockService, never()) registerWithUsername:....... password:.......];
I'm just not sure what to put in the ...... bits?
To specify that it's never called with any parameters, use the anything() matcher:
[verify(mockService, never()) registerWithUsername:(id)anything() password:(id)anything()];