• Andrey (6/27) Aug 18 2019 Here in tester I want to alias a template method and call it on
• rjframe (35/38) Aug 18 2019 I don't think you can alias an object method directly; three methods I

Andrey <saasecondbox yandex.ru> writes:

Hello,
I can't compile this piece of code:
 struct Object
 {
     void run(wstring ending, uint index)(int number)
     {
 
     }
 }
 
 void tester(alias callback, T)(int number, T object = null)
 {
     static if(is(T == typeof(null))) alias handler = callback;
     else auto handler(wstring ending, uint index) = 
 object.callback!(ending, index);
         	handler!("rfv", 5)(word);
 }
 
 void main()
 {
     Object obj;
     tester!(Object.run)(10, &obj);
 }

Here in tester I want to alias a template method and call it on 
object if this object isn't null. But I don't understand how to 
do it.
How to solve the problem?

rjframe <dlang ryanjframe.com> writes:

On Sun, 18 Aug 2019 19:17:16 +0000, Andrey wrote:

 Here in tester I want to alias a template method and call it on object
 if this object isn't null. But I don't understand how to do it.
 How to solve the problem?

I don't think you can alias an object method directly; three methods I 
know of:

---
struct Struct {
    void run(int number) {
        import std.stdio;
        writeln("run ", number);
    }
}

// Pass the object itself.
void func1(alias obj)(int number) if (isFunction!(obj.run)) {
    obj.run(number);
}

// Pass the object and the name of the method.
void func2(alias obj, string method)(int number)
        if (__traits(compiles, "obj." ~ method ~ "(number);")) 
{
    mixin("obj." ~ method ~ "(number);");   
}

// Pass the method at runtime.
void func3(void delegate(int) f, int number) {
    f(number);
}

void main() {
    Struct obj;
    func1!(obj)(1);
    func2!(obj, "run")(2);
    func3(&obj.run, 3);
}
---

Also, you don't want to name something "Object"; the base class is called 
Object -- the struct shadows it but you may run into some bug or confusion 
later.

--Ryan