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）
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)