从文件创建字符串

NSString *path = [[NSBundlemainBundle] pathForResource:@"string.text"ofType:nil];

NSString *string = [[NSString alloc] initWithContentsOfFile:path];

 

用字符串创建字符串，并写入到文件  

NSString *str = [[NSString alloc] initWithString:@"This is a String!"]; NSString *path = @"string.text";     [astring writeToFile: path atomically: YES];

 

compare方法(comparer返回的三种值)    

NSString *string01 = @"This is a String!"; NSString *string02 = @"This is a String!";     [string01 compare:string02] == NSOrderedSame;    //NSOrderedSame判断两者内容是否相同 NSString *string01 = @"This is a String!"; NSString *string02 = @"this is a String!"; [string01 compare:string02] == NSOrderedAscending;   //NSOrderedAscending判断两对象值的大小(按字母顺序进行比较，string02大于string01为真) NSString *string01 = @"this is a String!"; NSString *string02 = @"This is a String!"; [string01 compare:string02] == NSOrderedDescending;   //NSOrderedDescending判断两对象值的大小(按字母顺序进行比较，string02小于string01为真)

 

不考虑大小写比较字符串

NSString *string01 = @"this is a String!"; NSString *string02 = @"This is a String!"; [astring01 caseInsensitiveCompare:astring02] == NSOrderedSame;    //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)NSString *string01 = @"this is a String!"; NSString *string02 = @"This is a String!"; [string01 compare:string02 options:NSCaseInsensitiveSearch | NSNumericSearch] == NSOrderedSame;    //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。

 

输出大写或者小写字符串

NSString *string = @"string";  [string uppercaseString];//大写 [string lowercaseString];//小写 [string capitalizedString];//首字母大小

 

-rangeOfString: 查找字符串某处是否包含其它字符串

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

 

-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];

 

-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];

 

-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)];（0为位置，4为长度）

 

-stringWithCapacity: //按照固定长度生成空字符串

NSMutableString *String; String = [NSMutableString stringWithCapacity:10];

 

-appendString: and -appendFormat: //两个字符串连接

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"]; [String1 appendString:@",This is a NSMutableString"]; [String1 appendFormat:[NSString stringWithFormat:@",This is a NSMutableString"]];

 

-insertString: atIndex: //在指定位置插入字符串

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a String"]; [String1 insertString:@"Yes! " atIndex:0];

 

 

-replaceCharactersInRange: withString: //用指定字符串替换字符串中某指定位置、长度的字符串

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"]; [String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];

 

-hasPrefix: //检查字符串是否以另一个字符串开头 

NSString *String1 = @"NSStringaslkjdlaksjdlkas"; [String1 hasPrefix:@"NSString"] [String1 hasSuffix:@"kas"]

 

扩展路径

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