Objective－C 笔记 字符串操作

　　这次总结下OC里一些对字符串的一些操作。

　　创建字符串对象时，会创建一个内容不可更改的对象，称为不可变对象。可以使用NSString类处理不可变字符串。你经常需要处理字符串并更改字符串中的字符。例如，可能希望从字符串中删除一些字符，或对字符串执行搜索替换操作。这种类型的字符串是使用NSMutableString类处理的。

 1 // 2 // main.m 3 // Number_String_List_15 4 // 5 // Created by SeanAstin on 15/12/30. 6 // Copyright © 2015年 SeanAstin. All rights reserved. 7 // 8  9 #import <Foundation/Foundation.h>10 11 int main(int argc, const char * argv[]) {12   @autoreleasepool {13     NSString *str1 = @"This is string A";14     NSString *str2 = @"This is string B";15     NSString *res;16     NSComparisonResult compareResult;17     18     //计算字符串中的值19     NSLog(@"Length of str1: %lu",[str1 length]);20     21     //将一个字符串复制到另一个字符串22     res = [NSString stringWithString:str1];23     NSLog(@"copy: %@",res);24     25     //将一个字符串复制到另一个字符串的末尾26     str2 = [str1 stringByAppendingString:str1];27     NSLog(@"Concatentation: %@",str2);28     29     //验证两个字符串是否相等30     if([str1 isEqualToString:res] == YES)31       NSLog(@"str1 == res");32     else33       NSLog(@"str1 != res");34     35     //验证一个字符串是否小于、等于或大于另一个字符串36     compareResult = [str1 compare:str2];37     if(compareResult == NSOrderedAscending)38       NSLog(@"str1 < str2");39     else if(compareResult == NSOrderedSame)40       NSLog(@"str1 == str2");41     else//必须是NSorderedDescending42       NSLog(@"str1 > str2");43     44     //将字符串转换为大写45     res = [str1 uppercaseString];46     NSLog(@"Uppercase conversion: %s",[res UTF8String]);47     48     //将字符串转换为小写49     res = [str1 lowercaseString];50     NSLog(@"Lowercase conversion: %@",res);51   }52   return 0;53 }

 1 // 2 // main.m 3 // Number_String_List_15 4 // 5 // Created by SeanAstin on 15/12/30. 6 // Copyright © 2015年 SeanAstin. All rights reserved. 7 // 8  9 #import <Foundation/Foundation.h>10 11 int main(int argc, const char * argv[]) {12   @autoreleasepool {13     NSString *str1 = @"This is string A";14     NSString *str2 = @"This is string B";15     NSString *res;16     NSRange subRange;17     18     //从字符串中提取前3个字符19     res = [str1 substringToIndex:3];20     NSLog(@"First 3 chars of str1: %@",res);21     22     //提取从索引5开始直到结尾的子字符串23     res = [str1 substringFromIndex:5];24     NSLog(@"Chars from index 5 of str1: %@",res);25     26     //提取从索引8开始索引到13的子字符串（6个字符）27     res = [[str1 substringFromIndex:8] substringToIndex:6];28     NSLog(@"Chars from index 8 through 13: %@",res);29     30     //更简单的方法31     res = [str1 substringWithRange:NSMakeRange(8, 6)];32     NSLog(@"Chars from index 8 through 13: %@",res);33     34     //从另一个字符串中查找一个字符串35     subRange = [str1 rangeOfString:@"string A"];36     NSLog(@"String is at index %lu, length is %lu",subRange.location,subRange.length);37     subRange = [str1 rangeOfString:@"string B"];38     if(subRange.location == NSNotFound)39       NSLog(@"String not found");40     else41       NSLog(@"String is at index %lu, length is %lu",subRange.location,subRange.length);42     43   }44   return 0;45 }

　　NSMutableString类可以用来创建可以更改字符的字符串对象。因为是 NSString类的子类，所以可以使用NSString类的所有方法。

　　在讲述可变于不可变字符串对象时，我们谈到了更改字符串中的实际字符。任意一个可变或不可变字符串对象在程序执行期间，总是可以被设为完全不同的字符串对象的。

 1 // 2 // main.m 3 // Number_String_List_15 4 // 5 // Created by SeanAstin on 15/12/30. 6 // Copyright © 2015年 SeanAstin. All rights reserved. 7 // 8  9 #import <Foundation/Foundation.h>10 11 int main(int argc, const char * argv[]) {12   @autoreleasepool {13     NSString *str1 = @"This is string A";14     NSString *search,*replace;15     NSMutableString *mstr;16     NSRange substr;17     18     //从不可变字符串创建可变字符串19     20     mstr = [NSMutableString stringWithString:str1];21     NSLog(@"%@",mstr);22     23     //插入字符24     [mstr insertString: @" mutable" atIndex:7];25     NSLog(@"%@",mstr);26     27     //插入末尾进行有效拼接28     [mstr insertString:@" and string B" atIndex:[mstr length]];29     NSLog(@"%@",mstr);30     31     //直接使用appendString32     [mstr appendString:@" and string C"];33     NSLog(@"%@",mstr);34     35     //根据范围删除子字符串36     [mstr deleteCharactersInRange:NSMakeRange(16, 13)];37     NSLog(@"%@",mstr);38     39     //查找然后将其删除40     substr = [mstr rangeOfString:@"string B and "];41     if(substr.location != NSNotFound){42       [mstr deleteCharactersInRange:substr];43       NSLog(@"%@",mstr);44     }45     46     //直接设置为可变的字符串47     [mstr setString:@"This is string A"];48     NSLog(@"%@",mstr);49     50     //替换一些字符51     [mstr replaceCharactersInRange:NSMakeRange(8, 8) withString:@"a mutable string"];52     NSLog(@"%@",mstr);53     54     //查找和替换55     search = @"This is";56     replace = @"An example";57     substr = [mstr rangeOfString: search];58     if(substr.location != NSNotFound){59       [mstr replaceCharactersInRange:substr withString:replace];60       NSLog(@"%@",mstr);61     }62     63     //查找和替换所有匹配项64     search = @"a";65     replace = @"X";66     substr = [mstr rangeOfString:search];67     while(substr.location != NSNotFound){68       [mstr replaceCharactersInRange:substr withString:replace];69       substr = [mstr rangeOfString:search];70       71     }72     NSLog(@"%@",mstr);73   }74   return 0;75 }

原标题：Objective－C 笔记 字符串操作

关键词：