1.2 向Console写入信息

1、问题

测试代码的时候，想能够向console中写一些值。对象和原始类型都能够用NSLog报告出来，但是它们都有着自己的字符串格式化器。

 

2、解决方案

将对象以及原始值替换进NSLog，就能够报告这些变量的值。

 

3、原理

NSLog(@"myCharacter = %c and myInteger = %i", myCharacter, myInteger);

 

Table 1-1. List of Specifiers Used with NSLog 

Specifier               Data Type 

%@                      Objective-C object (looks at description method) 

%d, %D, %i           Int (signed 32-bit integer) 

%u, %U                Unsigned int (unsigned 32-bit integer) 

%f                         Double (64-bit floating point number) 

%e                        Double (64-bit floating point number in scientific notation) 

%c                        Unsigned char (unsigned 8-bit character) 

%C                       Unichar (16-bit character) 

%p                        Pointer (printed in hexadecimal) 

%%                       Escape character so you can print the % sign 

 

4、代码

#import <Foundation/Foundation.h>

int main(int argc, const char* argv[]) {

    @autoreleasepool {

        // To print out primitive types:

        int myInteger = 1;

        NSLog(@"myInteger = %i", myInteger); // Int (signed 32-bit integer) 

        float myFloatingPointNumber = 2;

        // Double (64-bit floating point number) 

        NSLog(@"myFloatingPointNumber = %f", myFloatingPointNumber); 

        NSLog(@"myFloatingPointNumber in scientific notation = %e", myFloatingPointNumber);

        

        char myCharacter = 'A';

        NSLog(@"myCharacter = %c", myCharacter); // Unsigned char (unsigned 8-bit character) 

      

        // To print out the % symbol

        NSLog(@"Percent Sign looks like %%");

 

        // To print out Objective-C objects

        NSString *myString = @"My String";

        NSLog(@"myString = %@", myString);

        NSLog(@"myString's pointer = %p", myString);

       

        // To print out a series of values

        NSLog(@"myCharacter = %c and myInteger = %i", myCharacter, myInteger);

    }

    return 0;

}