ARC 下处理内存暴涨的一个解决办法

for (int i = 0; i < 1000000000; i++) {
        
        NSString *s = @"ABC";
        s = [s lowercaseString];
        s = [s stringByAppendingString:@"ac"];
        NSLog(@"%@", s);
    }

 for (int i = 0; i < 1000000000; i++) {
        
        @autoreleasepool {
            
            NSString *s = @"ABC";
            s = [s lowercaseString];
            s = [s stringByAppendingString:@"ac"];
            NSLog(@"%@", s);
        }
    }