ObjectC快速入门教程(2)---字符串

背景

本文主要介绍Object C里使用频率比较高的NSString及NSMutableString两个类的使用(前者为不可变字符串类，后者为可变字符串类)及两者的常用方法.

一,NSString的使用

1.字符串比较

可以直接使用compare函数得到NSComparisonResult结果:

  //NSOrderedAscending 递增, NSOrderedSame 相等, NSOrderedDescending 递减        NSString *str1 = [NSString stringWithFormat:@"%@", @"hello world"];        NSString *str2 = [NSString stringWithUTF8String:"hello world"];        NSComparisonResult result = [str1 compare:str2];        if(result == NSOrderedAscending){            NSLog(@"str1 小于 str2");        }else if(result == NSOrderedSame){            NSLog(@"str1 等于 str2");        }else if(result == NSOrderedDescending){            NSLog(@"str1 大于 str2");        }

2.不区分大小写比较

      //1.1不区分大小写进行比较        NSComparisonResult result2 = [str1 caseInsensitiveCompare:str2];        //1.2不区分大小写的另外一种写法        NSComparisonResult result3 = [str1 compare:str2 options:NSCaseInsensitiveSearch];        NSLog(@"result3 = %li", result3);

3.判断字符串对象是否相等

isEqualToString

4.字符串开头结尾判断

   //1.4字符串开头判断        BOOL ret = NO;        NSString *str3 = @"www.baidu.com baidu uuu";        ret = [str3 hasPrefix:@"www"];        NSLog(@"ret = %d", ret);        //1.5字符串结尾判断        ret = [str3 hasSuffix:@"com"];        if(ret == YES){            NSLog(@"%@ 以com结尾", str3);        }

5.字符串拼接

NSString *str4 = @"www";        NSString *str11 = [str4 stringByAppendingString:@".baidu.com"];        NSLog(@"str11 = %@", str11);        NSString *str12 = [str4 stringByAppendingFormat:@"rest%d%s", 123, "hello"];        NSLog(@"str11 = %@", str12);

6.字符串提取

NSString *str13 = [str3 substringFromIndex:4]; //从起始位置截取到结束        NSLog(@"str13 = %@", str13);        NSLog(@"test = %@", [str3 substringToIndex:4]); //不包含指定位置        NSLog(@"test = %@", [str3 substringWithRange:NSMakeRange(4, 3)]);//起始位置和长度

7.字符串查找

   NSRange rage = [str3 rangeOfString:@"baidu"];        //static const NSInteger NSNotFound = NSIntegerMax;        if(rage.location != NSNotFound){            NSLog(@"loc = %li, lenth = %li", rage.location, rage.length);        }        //倒序查找        NSRange rage2 = [str3 rangeOfString:@"baidu" options:NSBackwardsSearch];        if(rage2.location != NSNotFound){            NSLog(@"loc = %li, lenth = %li", rage2.location, rage2.length);        }        //指定范围查找        NSRange rage3 = [str3 rangeOfString:@"baidu" options:NSLiteralSearch range:NSMakeRange(4, 4)];        if(rage3.location == NSNotFound){            NSLog(@"未查到...");        }

8.字符串大小写转换

  NSString *str = @"hello,World,test";        NSLog(@"%@", [str uppercaseString]); //小写转大写        NSLog(@"%@", [str lowercaseString]); //大写转小写        NSLog(@"%@", [str capitalizedString]); //每个单词的小写转大写

9.字符串数值转换

 NSString *test = @"1234";        NSLog(@"test = %i", [test intValue]); //转int        NSLog(@"test = %li", [test integerValue]);//转NSInteger对象        NSLog(@"test = %.2f", [test floatValue]);

10.字符串置换

     NSString *t1 = @"Hello, how are you!";        NSString *t2 = [t1 stringByReplacingCharactersInRange:[t1 rangeOfString:@"how"] withString:@"howw"];        //替换元字符串出现的所有目标字符串        NSString *t3 = [t1 stringByReplacingOccurrencesOfString:@"how" withString:@"howwww"];        NSLog(@"t3 = %@, 原始 = %@", t3, t1);

11.文件的输入输出

  NSError *error = nil;        NSString *tt1 = [NSString stringWithContentsOfFile:@"/Users/yanzi/Desktop/1.txt" encoding:NSUTF8StringEncoding error:&error];        if(error){            NSLog(@"error = %@", error);        }else{            NSLog(@"tt1 = %@", tt1);        }        //NSString写入文件        NSString *tt2 = @"中国人";        BOOL saveRet = [tt2 writeToFile:@"/Users/yanzi/Desktop/2.txt" atomically:YES encoding:NSUTF8StringEncoding error:nil];        if(saveRet){            NSLog(@"写入成功");        }else{            NSLog(@"写入失败");        }

二,NSMutableString的使用

1.创建和拼接

NSMutableString *mS1 = [NSMutableString stringWithUTF8String:"李小龙"];        [mS1 appendString:@",中国人"];        NSLog(@"mS1 = %@", mS1);        //创建指定容量大小的可变字符串对象        //等于@""，空字符串对象，不是nil        NSMutableString *ms2 = [[NSMutableString alloc]initWithCapacity:20];

2.插入字符串

[mS1 insertString:@"hello" atIndex:0];//增加字符串

3.删除指定范围的字符串

[mS1 deleteCharactersInRange:NSMakeRange(0, 2)]; 

4.重置字符串

[mS1 setString:@"中国人民"];

5.用传入的字符串替换指定范围内的字符

[mS1 replaceCharactersInRange:NSMakeRange(0, 2) withString:@"美国"];        NSLog(@"mS1 = %@", mS1);        [mS1 replaceOccurrencesOfString:@"美国" withString:@"中国" options:NSLiteralSearch range:NSMakeRange(0, [mS1 length])];        NSLog(@"mS1 = %@", mS1);

系列代码已上传github