目标C ..中的可变字符串初始化问题 [英] mutable string initialization problem in Objective C ..

问题描述

int main (int argc, const char * argv[])
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    NSMutableString *str1;
    [str1 setString:@"again"];
    NSLog(@"string is -- %@",str1);   // It prints " string is -- (null) " 
    [str1 release];
    [pool drain];
    return 0;
}

-------------------------------------------------- ----------------------------------

------------------------------------------------------------------------------------

int main (int argc, const char * argv[])
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    NSMutableString *str1;
    
    str1 = [NSMutableString stringWithString:@"hello again "]; // By adding this 
   [str1 setString:@"again"];                // Now this statements works properly .
    NSLog(@"string is -- %@",str1);    
    [str1 release];
    [pool drain];
    return 0;
}

我不明白为什么如果我先使用setString方法，str1没有初始化?

I can not understand why if I use setString method first, str1 is not initializing??

推荐答案

别忘了初始化NSMutableString

NSMutableString * str1 = [[NSMutableString alloc] init];

Don''t forget init NSMutableString

NSMutableString *str1 = [[NSMutableString alloc]init];

这篇关于目标C ..中的可变字符串初始化问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！