iOS autoreleasepool

• 一般当有处理大量临时对象时，如果不注意会造成内存暴增，可以使用 autoreleasepool 进行优化
• 一下代码时计算内存使用情况

// 计算当前内存
double getMemoryUsage(void) {
    struct task_basic_info info;
    mach_msg_type_number_t size = sizeof(info);
    kern_return_t kerr = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)&info, &size);
    double memoryUsageInMB = kerr == KERN_SUCCESS ? (info.resident_size / 1024.0 / 1024.0) : 0.0;
    return memoryUsageInMB;
}

• 比如如下创建大量对象

NSLog(@" 内存 - %f ",getMemoryUsage()); // 内存 - 73.328125
    for (int i = 0; i < 500000; i++) {
        NSNumber *num = [NSNumber numberWithInt:i];
        NSString *str = [NSString stringWithFormat:@"%d ", i];
        [NSString stringWithFormat:@"%@%@", num, str];
    }
    NSLog(@" 内存 - %f ",getMemoryUsage()); // 内存 - 95.750000 

• 使用 autoreleasepool

NSLog(@" 内存 - %f ",getMemoryUsage()); // 内存 - 73.339844
    for (int i = 0; i < 500000; i++) {
        @autoreleasepool {
            NSNumber *num = [NSNumber numberWithInt:i];
            NSString *str = [NSString stringWithFormat:@"%d ", i];
            [NSString stringWithFormat:@"%@%@", num, str];
        }
    }
    NSLog(@" 内存 - %f ",getMemoryUsage()); // 内存 - 73.339844