makeObjectsPerformSelector

makeObjectsPerformSelector.m

#import <UIKit/UIKit.h>

int main(int argc, char *argv[])
{
    @autoreleasepool {
        UIView* superView = [[UIView alloc] initWithFrame:CGRectZero];
        
        for(int i = 0; i < 10; i++){
            UIView* view = [[UIView alloc] initWithFrame:CGRectZero];
            [superView addSubview:view];
        }
        
        NSLog(@"count = %d", [superView.subviews count]);
        [superView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
        NSLog(@"count = %d", [superView.subviews count]);
    }
}

2011-09-16 09:44:47.526 Hoge100[1529:40b] count = 10
2011-09-16 09:44:47.527 Hoge100[1529:40b] count = 0


makeObjectsPerformSelector:
Sends to each object in the array the message identified by a given selector, 
starting with the first object and continuing through the array to the last object.

- (void)makeObjectsPerformSelector:(SEL)aSelector
Parameters
aSelector
A selector that identifies the message to send to the objects in the array. 
The method must not take any arguments, 
and must not have the side effect of modifying the receiving array.
Discussion
This method raises an NSInvalidArgumentException if aSelector is NULL.

Availability
Available in iOS 2.0 and later.
See Also
– makeObjectsPerformSelector:withObject:
Related Sample Code
LazyTableImages
Declared In
NSArray.h


@interface NSArray (NSExtendedArray)
- (void)makeObjectsPerformSelector:(SEL)aSelector;
- (void)makeObjectsPerformSelector:(SEL)aSelector withObject:(id)argument;


@interface NSSet (NSExtendedSet)
- (void)makeObjectsPerformSelector:(SEL)aSelector;
- (void)makeObjectsPerformSelector:(SEL)aSelector withObject:(id)argument;

NSArray -(void)makeObjectsPerformSelector; でNSArrayが持っている全てのObjectに対してmethodを実行できる。

こういう、表示が関係ないコードの場合は、main関数が書いてあるとすぐに実行できていいよね。

以下の2つみたいにループした場合と同じことやってるけどmakeObjectsPerformSelectorは1行で楽という認識になった。
あと複雑な処理の場合はmakeObjectsPerformSelectorの方がスコープが閉じられていいってメリットもあるのかな？

NSLog(@"count = %d", [superView.subviews count]);
for (UIView *view in superView.subviews) {
  [view removeFromSuperview];
}
NSLog(@"count = %d", [superView.subviews count]);

NSLog(@"count = %d", [superView.subviews count]);
NSEnumerator *viewEnumerator = [superView.subviews objectEnumerator];
UIView *view;
while (view = [viewEnumerator nextObject]) {
  [view removeFromSuperview];
}
NSLog(@"count = %d", [superView.subviews count]);

1行でできることを5行で書かれると、ソース読むときに何か意図があるのかな？と思うので
読むやすくしてほしいよねー、というだけだったり。

Blocks対応後は、

• enumerateObjectsUsingBlock:
• enumerateObjectsWithOptions:usingBlock:
• enumerateObjectsAtIndexes:options:usingBlock:

も良さそうです。

それらを使うと、Rubyのmapっぽい感じになりますね。