How to create an "array of selectors"

Question

I'm using the iPhone SDK (3.0) and I'm trying to create an array of selectors to invoke a variety of methods within one class.

Obviously, I'm doing something wrong (I think @selector isn't considered a class and so stuffing them into an NSArray isn't working).

I tried this, but it's obviously wrong.

Is there a simple way to have an array of selectors like this? Or is there a better way to iterate through a collection of methods?

selectors = [NSArray arrayWithObjects:
                          @selector(method1),
                          @selector(method2),
                          @selector(method3),
                          @selector(method4),
                          @selector(method5),
                          @selector(method6),
                          @selector(method7), nil];

for (int i = 0; i < [selectors count]; i++) {
    if ([self performSelector:[selectors objectAtIndex:i]]) // do stuff;
}

moribvndvs · Accepted Answer · 2012-06-20 04:22:09Z

80

Could you store strings and use NSSelectorFromString?

From the docs

NSSelectorFromString

Returns the selector with a given name.

SEL NSSelectorFromString (
   NSString *aSelectorName
);

edited Jun 20, 2012 at 4:22

moribvndvs

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answered Feb 9, 2010 at 3:28

Jesse Anderson

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2 Comments

Aleks N. Over a year ago

Not an appropriate solution for when just an array of selectors is needed.

DawnSong Over a year ago

NSPointerArray is better.

DenNukem · Accepted Answer · 2010-02-09 16:03:11Z

43

This creates an object out of selector:

[NSValue valueWithPointer:@selector(x)]

answered Feb 9, 2010 at 16:03

DenNukem

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3 Comments

Dean Kelly Over a year ago

How would you go about extracting the selector from this to be used by performSelector:?

ABCD.ca Over a year ago

@DeanKelly answered here stackoverflow.com/questions/575055/… by terry franguiadakis

DawnSong Over a year ago

Type cast is needed, as follows, SEL x = (SEL)selectorValue.pointerValue;

kennytm · Accepted Answer · 2010-02-09 16:12:13Z

37

Why not just use a simple C array?

static const SEL selectors[] = {@selector(method1),
                                ....
                                @selector(method7)};

...

for (int i = 0; i < sizeof(selectors)/sizeof(selectors[0]); i++) {
  [self performSelector:selectors[i]];
  // ....
}

answered Feb 9, 2010 at 16:12

kennytm

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1 Comment

Aleks N. Over a year ago

Good, but static is not needed here (initializer is not a compile-time constant).

Morrowless · Accepted Answer · 2011-05-30 04:42:37Z

13

You can also create an array of NSInvocations. This is handy if you need an argument to go with your selector.

NSMethodSignature *sig = [[yourTarget class] instanceMethodSignatureForSelector:yourSEL];
NSInvocation *inv = [NSInvocation invocationWithMethodSignature:sig];
[inv setTarget:yourTarget];
[inv setSelector:yourSEL];
[inv setArgument:&yourObject atIndex:2]; // Address of your object

edited May 30, 2011 at 4:42

answered May 30, 2011 at 4:13

Morrowless

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1 Comment

DawnSong Over a year ago

NSInvocation is too expensive.

big_m · Accepted Answer · 2014-03-27 03:27:56Z

1

If the list is static, I'd go with KennyTM's solution, but if you need a dynamic array or set, another option, besides storing the selector string, is to create an object with an SEL property or ivar, and store that.

@interface SelectorObject : NSObject
@property (assign, readonly, nonatomic) SEL selector;
- (id)initWithSelector:(SEL)selector;
@end

@implementation SelectorObject
- (id)initWithSelector:(SEL)selector {
  self = [super init];
  if (self) {
    _selector = selector;
  }
  return self;
}
@end

You could then add a perform method to the class as well, and implement the method call there.

answered Mar 27, 2014 at 3:27

big_m

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Comments

DawnSong · Accepted Answer · 2019-05-06 03:42:42Z

1

I'd like to supplement two methods of storing selectors in an array,

First, NSPointerArray can store opaque pointer, such as SEL, as Apple doc said,

NSPointerArray *selectors = [[NSPointerArray alloc] initWithOptions: NSPointerFunctionsOpaqueMemory];
[selectors addPointer:@selector(onSendButton:)];
[button addTarget: self action:[selectors pointerAt:0] forControlEvents:UIControlEventTouchUpInside];

Second, C-style array is much simpler,

SEL selectors[] = { @selector(onSendButton:) };
[button addTarget: self action:selectors[0] forControlEvents:UIControlEventTouchUpInside];

Choose any as you wish.

edited May 6, 2019 at 3:42

answered Jan 8, 2019 at 9:43

DawnSong

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