Objective-C字符串类NSString使用方法是本文要介绍的内容，内容不多，是用代码来讲解关于字符串的使用，不多说，来看内容。开发过程中，我们会遇到很多关于字符串的操作，它是一个常用的数据类型，下面对它的用法进行了汇总：

    //1、创建常量字符串。  
    NSString *astring = @"This is a String!";  
 
    //2、创建空字符串，给予赋值。  
 
    NSString *astring = [[NSString alloc] init];  
    astring = @"This is a String!";  
    NSLog(@"astring:%@",astring);  
  [astring release];  
 
//3、在以上方法中，提升速度:initWithString方法  
 
    NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];  
    NSLog(@"astring:%@",astring);  
    [astring release];  
 
 //4、用标准c创建字符串:initWithCString方法  
 
    char *Cstring = "This is a String!";  
    NSString *astring = [[NSString alloc] initWithCString:Cstring];  
    NSLog(@"astring:%@",astring);  
    [astring release];  
 
    //5、创建格式化字符串:占位符（由一个%加一个字符组成）  
 
    int i = 1;  
    int j = 2;  
    NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];  
    NSLog(@"astring:%@",astring);  
    [astring release];  
 
    //6、创建临时字符串  
 
    NSString *astring;  
    astring = [NSString stringWithCString:"This is a temporary string"];  
    NSLog(@"astring:%@",astring);  
 
    NSString *path = @"astring.text";  
    NSString *astring = [[NSString alloc] initWithContentsOfFile:path];  
    NSLog(@"astring:%@",astring);  
    [astring release];  
 
    NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];  
    NSLog(@"astring:%@",astring);  
    NSString *path = @"astring.text";      
    [astring writeToFile: path atomically: YES];  
    [astring release];      
 
    //用C比较:strcmp函数  
 
    char string1[] = "string!";  
    char string2[] = "string!";  
    if(strcmp(string1, string2) = = 0)  
    {  
        NSLog(@"1");  
    }  
 
   //isEqualToString方法      
    NSString *astring01 = @"This is a String!";  
    NSString *astring02 = @"This is a String!";  
    BOOL result = [astring01 isEqualToString:astring02];  
    NSLog(@"result:%d",result);  
 
   //compare方法(comparer返回的三种值)      
    NSString *astring01 = @"This is a String!";  
    NSString *astring02 = @"This is a String!";      
    BOOL result = [astring01 compare:astring02] = = NSOrderedSame;      
    NSLog(@"result:%d",result);      
    //NSOrderedSame 判断两者内容是否相同  
 
    NSString *astring01 = @"This is a String!";  
    NSString *astring02 = @"this is a String!";  
    BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;      
    NSLog(@"result:%d",result);  
    //NSOrderedAscending 判断两对象值的大小(按字母顺序进行比较，astring02大于astring01为真)  
 
    NSString *astring01 = @"this is a String!";  
    NSString *astring02 = @"This is a String!";  
    BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;      
    NSLog(@"result:%d",result);       
    //NSOrderedDescending 判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为真)  
//不考虑大 小写比较字符串1  
    NSString *astring01 = @"this is a String!";  
    NSString *astring02 = @"This is a String!";  
    BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;      
    NSLog(@"result:%d",result);       
    //NSOrderedDescending判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为真)  
//如何判断字符串为空  
NSString *urlString = [urlInput stringValue];  
if (!urlString) {   
NSLog( @”NO INPUT.” );  
} else {   
if ([urlString length] == 0 ) {  
NSLog( @”NO INPUT.” );  
} else {  
}  
}   
}