Xcode 警告：格式指定类型“long”，但参数类型为“int _Nullable”
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/33121583/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Xcode warning: Format specifies type 'long' but the argument has type 'int _Nullable'
提问by bbjay
I get this warning for the following line of code:
我收到以下代码行的警告：
NSLog(@"selected segment: %li", _segmentControl.selectedSegmentIndex);
The property selectedSegmentIndexis of type NSInteger.
该属性selectedSegmentIndex为 类型NSInteger。
If I change the format to %ii get the following warning:
如果我将格式更改为%i我收到以下警告：
Format specifies type 'int' but the argument has type 'long _Nullable'
Are there any new format specifiers for Nullable types or is this just a bug in Xcode 7?
Nullable 类型是否有任何新的格式说明符，或者这只是 Xcode 7 中的一个错误？
回答by Vive
You should type:
你应该输入：
NSLog(@"selected segment: %li", (long)_segmentControl.selectedSegmentIndex);
Because NSInteger has a different length in 32 and 64bit architecture. Previously you didn't see the warning, because probably you was compiling only against 64 bit architecture.
因为 NSInteger 在 32 位和 64 位架构中的长度不同。以前您没有看到警告，因为您可能只针对 64 位架构进行编译。
I'd also advise to read Apple Article, as there are new specifiers in Xcode 7 (among others nullableand nonnull).
我还建议阅读Apple 文章，因为 Xcode 7 中有新的说明符（以及nullable和nonnull）。
To answer your doubts from the comment, please refer to this Apple document, where they state the following:
要从评论中回答您的疑问，请参阅此Apple 文档，其中说明了以下内容：
Type Specifiers
Script action: Warns about potential problems; may generate false negatives.
Typically, in 32-bit code you use the %d specifier to format int values in functions such as printf, NSAssert, and NSLog, and in methods such as stringWithFormat:. But with NSInteger, which on 64-bit architectures is the same size as long, you need to use the %ld specifier. Unless you are building 32-bit like 64-bit, these specifiers generates compiler warnings in 32-bit mode. To avoid this problem, you can cast the values to long or unsigned long, as appropriate. For example:
NSInteger i = 34; printf("%ld\n", (long)i);
类型说明符
脚本操作：警告潜在问题；可能会产生假阴性。
通常，在 32 位代码中，您在 printf、NSAssert 和 NSLog 等函数以及 stringWithFormat: 等方法中使用 %d 说明符格式化 int 值。但是对于 NSInteger，它在 64 位体系结构上的大小与 long 相同，您需要使用 %ld 说明符。除非您像 64 位一样构建 32 位，否则这些说明符会在 32 位模式下生成编译器警告。为避免此问题，您可以根据需要将值强制转换为 long 或 unsigned long。例如：
NSInteger i = 34; printf("%ld\n", (long)i);
回答by user1105951
Just want to add : I got this warning "suddenly" even when I did not change the code that made the warning for long time, and I did not understand why it's appear.
只想补充一下：即使我很长时间没有更改发出警告的代码，我也“突然”收到此警告，并且我不明白为什么会出现此警告。
The reason : "Generic iOS Device". when selected device or simulator, the warnings disappear.
原因：“通用iOS设备”。when selected device or simulator, the warnings disappear.
still, I add to the NSLog "(long)" to the variables. till then I only had "%ld", that turn the warning no matter what was selected (generic device, real device, simulator)
仍然，我将 NSLog "(long)" 添加到变量中。直到那时我只有“％ld”，无论选择什么都会发出警告（通用设备，真实设备，模拟器）
