@selector - With Multiple Arguments?

Question

I have been using @selector today for the first time and have not been able to work out how to do the following? How would you write the @selector

Answer 1

I had an issue where I needed to use the afterDelay along with multiple arguments to my @selector method. Solution? Use a wrapper function!

Say this is the function I want to pass to @selector:

-(void)myFunct:(NSString *)arg1 andArg:(NSString *)arg2 andYetAnotherArg:(NSString *)arg3;

Obviously, I can't even use withObject: withObject: here, so, make a wrapper!

-(void)myFunctWrapper:(NSArray *)myArgs {
    [self myFunct:[myArgs objectAtIndex:0] andArg:[myArgs objectAtIndex:1] andYetAnotherArg:[myArgs objectAtIndex:2]];
}

and use it by doing:

NSArray *argArray = [NSArray arrayWithObjects:string1,string2,string3,nil];
[self performSelector:@selector(myFunctWrapper:) withObject:argArray afterDelay:1.0];

This way I can have multiple arguments and use the selector with delay.

Answer 2

 

 - (id)performSelector:(SEL)aSelector
           withObject:(id)anObject  
           withObject:(id)anotherObject

From the Documentation:

This method is the same as performSelector: except that you can supply two arguments for aSelector. aSelector should identify a method that can take two arguments of type id. For methods with other argument types and return values, use NSInvocation.

so in your case you would use:

[self performSelector:@selector(printText:andMore:)
           withObject:@"Cake"
           withObject:@"More Cake"]

Answer 3

[self performSelector:@selector(printText:andMore) withObject:@"Cake" withObject:@"More Cake"];

Answer 4

As KennyTM pointed out, the selector syntax is

@selector(printText:andMore:)

You call it with

performSelector:withObject:withObject. 

... if you need more arguments or different types, you need to use NSIvocation

Answer 5

As an alternative for NSInvocation when you have more than two parameters, you can use NSObject's -methodForSelector: as in the following example:

SEL a_selector = ...
Type1 obj1 = ...
Type2 obj2 = ...
Type3 obj3 = ...
typedef void (*MethodType)(id, SEL, Type1, Type2, Type3);
MethodType methodToCall;
methodToCall = (MethodType)[target methodForSelector:a_selector];
methodToCall(target, a_selector, obj1, obj_of_type2, obj_of_type3);

Answer 6

Elaborating on Ben-Uri's answer, which can be written way shorter.

E.g. calling the UIView method - (CGPoint)convertPoint:(CGPoint)point toView:(UIView *)view can be done as follows:

SEL selector = @selector(covertPoint:toView:);
IMP method = [viewA methodForSelector:selector];
CGPoint pointInB = method(viewA, selector, pointInA, viewB);