下效的把NSMutableArray變成NSArray

我玫鄰辦法中部大概會(huì)用NSMutableArray,但是前來(lái)的時(shí)辰欲看別的進(jìn)出有來(lái)改我們的Array

   NSMutableArray *array1 = [@[] mutableCopy];
    for (int i = 0; i < 10000000; i++)
    {
        [array1 addObject:@(i)];
    }

    return array1;

那噶勘辰我們平強(qiáng)的做房嗲拷貝array1大概是逝世成一個(gè)新的array1

return [array1 copy];
return [NSArray arrayWithArray:array1];

那里呢,我們挨印了下光陽(yáng)

    NSMutableArray *array1 = [@[] mutableCopy];
    NSMutableArray *array2 = [@[] mutableCopy];

    PERF_ENTER_(init)
    for (int i = 0; i < 10000000; i++)
    {
        [array1 addObject:@(i)];
        [array2 addObject:@(i)];
    }
    PERF_LEAVE_(init)

    PERF_ENTER_(copy)
    NSArray *array3 = [array1 copy];
    PERF_LEAVE_(copy)
    NSLog(@"%@", [array3 class]);

    PERF_ENTER_(arrayWithArray)
    NSArray *array4 = [NSArray arrayWithArray:array1];
    PERF_LEAVE_(arrayWithArray)
    NSLog(@"%@", [array4 class]);

/*    
2015-01-07 00:57:36.869 JoinShow[1134:68543] +[XYPerformance recordName:andTime:] 'init' = 5.492105(s)
2015-01-07 00:57:37.125 JoinShow[1134:68543] +[XYPerformance recordName:andTime:] 'copy' = 0.255650(s)
2015-01-07 00:57:37.125 JoinShow[1134:68543] __NSArrayI
2015-01-07 00:57:37.373 JoinShow[1134:68543] +[XYPerformance recordName:andTime:] 'arrayWithArray' = 0.247696(s)
2015-01-07 00:57:37.373 JoinShow[1134:68543] __NSArrayI
*/

收明畸形卑せ個(gè)哪當(dāng)ツ倒array必要0.2s,罩窩經(jīng)是出有磕驏有及忍的光陽(yáng)了.必要對(duì)辦法盡行劣化.
紊的實(shí)量是甚么,勢(shì)兌們必要前來(lái)一個(gè)弗成變的array,是以我們可能曲接把 NSMutableArray 東西的isa 建改成 NSArray.

- (NSArray *)immutable
{
    object_setClass(self, [NSArray class]);
    return self;
}

    PERF_ENTER_(immutable)
    NSArray *array5 = [array2 immutable];
    PERF_LEAVE_(immutable)
    NSLog(@"%@", [array5 class]);
/*
2015-01-07 00:57:37.373 JoinShow[1134:68543] +[XYPerformance recordName:andTime:] 'immutable' = 0.000030(s)
2015-01-07 00:57:37.373 JoinShow[1134:68543] NSArray
*/

看下光陽(yáng),出有雅然快很多.
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閉于那多么做,咱只能道念法想法是好的.實(shí)際...