Objective-c确保var-arg参数的类型和计数正确 [英] Objective-c Ensure that var-arg parameters are of the correct type and count

问题描述

在Objective-C中，如何确保您的函数具有可变参数，且格式说明符与传递给functoin的实际参数对齐?

In objective-c how do you ensure that if you have a function that takes variable parameters that the format specifiers align with the actual parameters that are passed to the functoin?

推荐答案

这是通过使用NS_FORMAT_FUNCTION宏完成的.

This is done through the use of the NS_FORMAT_FUNCTION macro.

假设您具有这样的功能:

Let's say that you have a function like this:

LOG(int level,NSString *format,...);

级别是日志级别，而格式包含格式字符串，而变量参数是格式字符串的参数.

The level is the log level while the format contains the format string and the variable arguments are the parameters to the format string.

为了确保在编译时参数的数量和类型正确，一个函数定义如下:

In order to ensure at compile time that the count and type of the parameters is correct one defines the function as this:

LOG(int level,NSString *format,...) NS_FORMAT_FUNCTION(2,3);

请注意，此处的2和3指的是格式字符串的参数列表中的位置以及可变参数列表的开头.

Note that the 2 and 3 here refer to the position in the arguments list of the format string and the start of the variable parameter list.

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