使用for、forin和block遍历NSArray的效率的比较

#import <Foundation/Foundation.h>

extern uint64_t dispatch_benchmark(size_t count, void (^block)(void));
void processNumber(NSNumber *n);

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        
        // 创建一个数组并用随机数填充
        NSUInteger const capacity = 15;
        NSMutableArray *array = [NSMutableArray arrayWithCapacity:capacity];
        for (NSUInteger i = 0; i < capacity; ++i) {
            [array addObject:@(arc4random_uniform(100))];
        }
        
        size_t count = 10000000;
        // 使用for循环遍历数组
        uint64_t time1 = dispatch_benchmark(count, ^{
            for (NSUInteger i = 0; i < capacity; ++i) {
                processNumber(array[i]);
            }
        });
        NSLog(@"for = %lluns", time1);
        
        // 使用forin循环遍历数组
        uint64_t time2 = dispatch_benchmark(count, ^{
            for (NSNumber *num in array) {
                processNumber(num);
            }
        });
        NSLog(@"forin = %lluns", time2);
        
        // 使用block遍历数组
        uint64_t time3 = dispatch_benchmark(count, ^{
            [array enumerateObjectsUsingBlock:^(NSNumber *num, NSUInteger idx, BOOL *stop) {
                processNumber(num);
            }];
        });
        NSLog(@"block = %lluns", time3);
        
    }
    return 0;
}

void processNumber(NSNumber *n) {
    // code...
}

for = 326ns
forin = 237ns
block = 638ns

for = 20ns
forin = 106ns
block = 496ns