1、创建常量字符串
NSString *aString = @"hello";
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);
/*----------------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]);