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 else 33 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NSorderedDescending 42 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 else 41 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appendString 32 [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 }
