NSString concat在设备上不起作用

Question

我有一个小小的挑战。我使用下面的代码来连接一个NSString。在控制台上，输出是正常的，但在设备上却不起作用。我似乎不知道我错过了什么。

- (void)loadContent {
    getHTML = @"leap";
    NSLog(@"getHTML start: %@", getHTML);
    int showLeap = selectedLeap +1;
    NSString *leapString = [NSString stringWithFormat:@"%d", showLeap];

    if (showLeap<10) {
        getHTML = [getHTML stringByAppendingString:@"0"];
    }

    getHTML = [getHTML stringByAppendingString:leapString];
    getHTML = [getHTML stringByAppendingString:selectedMenu];
    NSLog(@"getHTML complete: %@", getHTML);

在模拟器上，输出为：

2015-06-03 12:11:57.619 iOS_TWW_EVOLUTION[917:582733] getHTML start: leap
2015-06-03 12:11:57.621 iOS_TWW_EVOLUTION[917:582733] getHTML complete: leap01_summary

在设备上，输出为：

2015-06-03 12:15:40.341 iOS_TWW_EVOLUTION[917:582733] getHTML start: leap
2015-06-03 12:15:40.346 iOS_TWW_EVOLUTION[917:582733] getHTML complete: getHTML complete: 

Answer 1

我找到了一个解决方案。奇怪的是NSString stringByAppendingString..。方法在设备上一直返回nil。这是我使用NSString stringWithFormat的解决方案...方法：

int showLeap = selectedLeap +1;
NSString *first = @"leap";
NSString *second = @""; if (showLeap<10) { second=@"0";}
NSString *third = [NSString stringWithFormat:@"%d", showLeap];
NSString *fourth = selectedMenu;
NSString *getHTML = [NSString stringWithFormat: @"%@%@%@%@", first, second, third, fourth];
NSLog(@"getHTML complete: %@", getHTML);