NSString常见用法

 1、创建常量字符串
 NSString *str = @"Hello World!";

 2、创建空字符串，给予赋值
 NSString *str = [[NSString alloc] init];
 str = @"Hello World!";
 [str release];

 3、initWithString方法
 NSString *str = [[NSString alloc] initWithString:@"Hello World!"];
 [str release];

 4、用标准c创建字符串:initWithCString方法
 char *Cstr = "This is a String!";
 NSString *str = [[NSString alloc] initWithCString:Cstr];
 [str release];

 5、创建格式化字符串:占位符%
 int i = ;
 int j = ;
 NSString *str = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];
 [str release];

 6、创建临时字符串
 NSString *str = [NSString stringWithCString:"Hello World"];

 7、从文件创建字符串
 NSString *path = [[NSBundlemainBundle] pathForResource:@"str.text"ofType:nil];
 NSString *str = [[NSString alloc] initWithContentsOfFile:path];
 NSLog(@"str:%@",str);
 [str release];

 8、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 = @"str.text";
 [str writeToFile: path atomically: YES];
 [str release];

 、isEqualToString方法
 NSString *str01 = @"This is a String!";
 NSString *str02 = @"This is a String!";
 BOOL result = [str01 isEqualToString:str02];
 NSLog(@"result:%d",result);

 10、compare方法(comparer返回的三种值)
 47 //NSOrderedSame判断两者内容是否相同
 NSString *str01 = @"This is a String!";
 NSString *str02 = @"This is a String!";
 BOOL result = [str01 compare:str02] == NSOrderedSame;
 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 *str01 = @"This is a String!";
 NSString *str02 = @"this is a String!";
 BOOL result = [str01 compare:str02] == NSOrderedAscending;
 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)
 NSString *str01 = @"this is a String!";
 NSString *str02 = @"This is a String!";
 BOOL result = [str01 compare:str02] == NSOrderedDescending;
 NSLog(@"result:%d",result); 

 11、不考虑大小写比较字符串
 NSString *str01 = @"this is a String!";
 NSString *str02 = @"This is a String!";
 BOOL result = [str01 caseInsensitiveCompare:str02] == NSOrderedSame;    //NSOrderedDescending判断两对象值的大小(按字母顺序进行比较，str02小于str01为真)
 NSLog(@"result:%d",result); 

 NSString *str01 = @"this is a String!";
 NSString *str02 = @"This is a String!";
 BOOL result = [str01 compare:str02

 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。
 NSLog(@"result:%d",result);

 12、输出大写或者小写字符串
 NSString *string1 = @"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

 13、-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 *str = [[NSString alloc] initWithString:[NSString stringWithFormat:@"Location:%i,Leight:%i",location,leight]];
 NSLog(@"str:%@",str);
 [str release];

 14、-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:];
 NSLog(@"string2:%@",string2);

 15、-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:];
 NSLog(@"string2:%@",string2);

 16、-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(, )];
 NSLog(@"string2:%@",string2);

 17、-stringWithCapacity: 按照固定长度生成空字符串
 NSMutableString *String;
 String = [NSMutableString stringWithCapacity:];

 18、-appendString: and -appendFormat: 把一个字符串接在另一个字符串的末尾
 NSMutableString *str1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];

 [str1 appendString:@", I will be adding some character"];

 [str1 appendFormat:[NSString stringWithFormat:@", I will be adding some character"]];

 NSLog(@"str1:%@",str1);

 19、-insertString: atIndex: 在指定位置插入字符串
 NSMutableString *str1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];

 [str1 insertString:@"Hi! " atIndex:];

 NSLog(@"str1:%@",str1);

 20、-setString:
 NSMutableString *str = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];

 [str setString:@"Hello Word!"];

 NSLog(@"str:%@",str);

 21、-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 *str = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];

 [str replaceCharactersInRange:NSMakeRange(, ) withString:@"That"];

 NSLog(@"str:%@",str);

 22、-hasPrefix: 检查字符串是否以另一个字符串开头
 NSString *str = @"NSStringInformation.txt";

 [str hasPrefix:@"NSString"] = =  ?  NSLog(@"YES") : NSLog(@"NO");

 [str hasSuffix:@".txt"] = =  ?  NSLog(@"YES") : NSLog(@"NO");

 23、扩展路径
 NSString *Path = @"~/NSData.txt";

 NSString *absolutePath = [Path stringByExpandingTildeInPath];

 NSLog(@"absolutePath:%@",absolutePath);

 NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);

 24、文件扩展名
 NSString *Path = @"~/NSData.txt";

 NSLog(@"Extension:%@",[Path pathExtension]);

  // 切割所有的参数
 NSArray *array = [str componentsSeparatedByString:@"&"];