objective-c中的NSString操作

//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）

   1):这类方法称为简便(convenience)方法或工厂方法，并且返回自动释放的对象，使用了自动释放池

   int i = 1;
    int j = 2;
    NSString *astring = [NSString stringWithFormat:@"%d.This is %i string!",i,j];
    NSLog(@"astring:%@",astring);
   

   2):这类方法虽然代码复杂一些，但性能比简便方法好

    int i = 1;
    int j = 2;
    NSString *astring = [[NSString alloc] initWithFormat::@"%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 {

 
}

 
} 
} 

 

 

Convert NSString to int

1	NSString *aNumberString = @"123";

2	int i = [aNumberString intValue];

 

Convert int to NSString

1	int aNumber = 123;

2	NSString *aString = [NSString stringWithFormat:@"%d", aNumber];