passing selector as a variable

LunarMoon · 02-19-2009, 04:11 PM

Hi,

I have a timer that has to fire 3 different methods: m1, m2 and m3.

I have a string called methodName that contains the name of the method that I have to fire.

What I am trying is this...

Code:

	NSTimer *timerStart = [[NSTimer scheduledTimerWithTimeInterval:0.5
	target:self
	selector:@selector( methodName )
	userInfo:nil	repeats:NO]
	retain];

	[timerStart release];

I need to pass the method name inside the timer's selector. Is that possible?

thanks for any help

SkylarEC · 02-19-2009, 04:15 PM

SEL yourVariable = @selector(yourSelector:);

LunarMoon · 02-19-2009, 04:28 PM

Quote:

Originally Posted by SkylarEC

SEL yourVariable = @selector(yourSelector

;

Thanks, but I am not sure if I understood that...

My string variable is formed like this...

Code:

// according to x value we will have m1, m2 or m3 as string.
NSString * methodName = [NSString stringWithFormat:@"m%@", x ];

SEL myMethod = @selector(methodName);

// then what?

NSTimer *myTimer = [[NSTimer scheduledTimerWithTimeInterval:0.5
	  target:self		selector:myMethod
	userInfo:nil	repeats:NO]		retain];
	[myTimer release];

???? this do not seems to work.
I am receiving an error message telling me that methodName variable is not being used...

RickMaddy · 02-19-2009, 04:41 PM

You can't pass a variable to @selector - you can only pass the actual name of a method.

Try the 'NSSelectorFromString' function instead.

**Kalimba** · 02-19-2009, 04:44 PM

Quote:

Originally Posted by LunarMoon

Thanks, but I am not sure if I understood that...

My string variable is formed like this...

Code:

// according to x value we will have m1, m2 or m3 as string.
NSString * methodName = [NSString stringWithFormat:@"m%@", x ];

SEL myMethod = @selector(methodName);

// then what?

NSTimer *myTimer = [[NSTimer scheduledTimerWithTimeInterval:0.5
	  target:self		selector:myMethod
	userInfo:nil	repeats:NO]		retain];
	[myTimer release];

???? this do not seems to work.
I am receiving an error message telling me that methodName variable is not being used...

I suspect that the "@selector(methodName)" in your code isn't doing what you think it's doing.

My understanding of the @selector(some_name_here) construct is that it's an Objective-C directive that instructs the compiler to build a selector with the named parameter. So "@selector(methodName)" builds a selector with the name "methodName", and that's it. The "methodName" used to build the selector has no association with the "methodName" variable you have declared in your code.

Is the "x" that you're using to determine your callback a persistent variable? If so, there is a perhaps a simple solution to this problem. Can you see it?

LunarMoon · 02-19-2009, 04:52 PM

ahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhh!!!!!!!!!!!!

thank you guys!!! you're the best!

SkylarEC · 02-19-2009, 04:58 PM

RickMaddy, I have had absolutely no problem on the iPhone setting the SEL variable and using it. That's why the SEL variable exists, after all.

Code:

//Create your selectors
SEL myMethod = @selector(aMethod:);
//etc...

/*____________________________The rest of your code.____________________________*/

//
aTimer = [NSTimer scheduledTimerWithTimeInterval: 0.75 target:self selector:myMethod userInfo:nil repeats:YES];

As you see, just set it and use it as you would any other variable.

RickMaddy · 02-19-2009, 05:17 PM

Sorry, you misunderstood my post. What you can't do is pass a variable to the @selector directive. Of course you can assign the result of @selector to a SEL variable. The part in the parentheses can't be a variable.

tkilmer · 02-19-2009, 05:18 PM

Lunar was originally trying to set the selector using an NSString. What you are doing is right, but if you want to set the selector based off of a string like Lunar originally attempted, Ricks solution is correct.