iOS 常用字符串的操作

//将NSData转化为NSString

 NSString* str = [[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding];

//将NSString 转化为NSData (NSString.h)

- (NSData *)dataUsingEncoding:(NSStringEncoding)encoding; 

---

//载一个字符串中删除一个字符或字符串

[_display deleteCharactersInRange:NSMakeRange(index_of_char_to_remove, 1)];

//数学转换为字符串

NSString *returnStr;
returnStr = [[NSNumber numberWithInt:row] stringValue]; 

//创建常量字符串。

  NSString *astring = @"This is a String!";              

//创建空字符串，给予赋值。

NSString *astring = [[NSString alloc] init];    
  astring = @"This is a String!";     
 [astring release];      
NSLog(@"astring:%@",astring);                      

//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];  

//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];                       

//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]; 

//创建临时字符串

  NSString *astring;    
  astring = [NSString stringWithCString:"This is a temporary string"];    
  NSLog(@"astring:%@",astring); 

从文件读取字符串:initWithContentsOfFile方法

 NSString *path = @"astring.text"; 
NSString *astring = [[NSString alloc] initWithContentsOfFile:path]; 
 NSLog(@"astring:%@",astring);   
   [astring release];  

写字符串到文件:writeToFile方法

NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];      
NSLog(@"astring:%@",astring);     
NSString *path = @"astring.text";      
 [astring writeToFile: path atomically: YES]; 
 [astring release]; 

比较两个字符串

 //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)

 //不考虑大小写比较字符串2      
NSString *astring01 = @"this is a String!";    
NSString *astring02 = @"This is a String!";    
BOOL result = [astring01 compare:astring02  options:NSCaseInsensitiveSearch | NSNumericSearch] = = NSOrderedSame;      
NSLog(@"result:%d",result);           
//NSCaseInsensitiveSearch:不区分大小写比较 NSLiteralSearch:进行完全比较，区分大小写 NSNumericSearch:比较字符串的字符个数，而不是字符值。  

改变字符串的大小写

NSString *string1 = @"A String";   
NSString *string2 = @"String";    
NSLog(@"string1:%@",[string1 uppercaseString]);//大写     
NSLog(@"string2:%@",[string2 lowercaseString]);//小写       
NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小  

在串中搜索子串

NSString *string1 = @"This is a string";     
NSString *string2 = @"string";    
NSRange range = [string1 rangeOfString:string2];  
int location = range.location;    
int leight = range.length;     
NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"Location:%i,Leight:%i",location,leight]];
NSLog(@"astring:%@",astring);   
 [astring release];        

抽取子串

 //-substringToIndex: 从字符串的开头一直截取到指定的位置，但不包括该位置的字符  
 NSString *string1 = @"This is a string";   
 NSString *string2 = [string1 substringToIndex:3];   
 NSLog(@"string2:%@",string2);                   

 //-substringFromIndex: 以指定位置开始（包括指定位置的字符），并包括之后的全部字符    
NSString *string1 = @"This is a string";      
NSString *string2 = [string1 substringFromIndex:3];
NSLog(@"string2:%@",string2);                   
 //-substringWithRange: //按照所给出的位置，长度，任意地从字符串中截取子串   
NSString *string1 = @"This is a string";      
NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
NSLog(@"string2:%@",string2);        

扩展路径

NSString *Path = @"~/NSData.txt";   
NSString *absolutePath = [Path stringByExpandingTildeInPath];
NSLog(@"absolutePath:%@",absolutePath);
NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);                   

文件扩展名

NSString *Path = @"~/NSData.txt";
NSLog(@"Extension:%@",[Path pathExtension]);  

原文出处xiaoou