iPhone objective-c字符串类NSString的使用


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 { 
 
} 
 
} 
}

补充：移动开发 , Android ,