Objective-C中使用NSString类操作字符串的方法小结

一、字符串切割
1、带节点的字符串，如@"<p>讨厌的节点<br/></p>"我们只想要中间的中文

处理方法：

nsstring *string1 = @"<p>讨厌的节点<br/></p>";
 
/*此处将不想要的字符全部放进characterset1中，不需另外加逗号或空格之类的，除非字符串中有你想要去除的空格，此处< p /等都是单独存在，不作为整个字符*/
 
nscharacterset *characterset1 = [nscharacterset charactersetwithcharactersinstring:@"<p/brh>"];
 
// 将string1按characterset1中的元素分割成数组
 
nsarray *array1 = [string1 componentsseparatedbycharactersinset:characterset1];
 
nslog(@"array = %@",array1);
 
for(nsstring *string1 in array1)
{
    if ([string1 length]>0) {
        
        // 此处string即为中文字符串
 
        nslog(@"string = %@",string1);
    }
}

打印结果：

2016-01-17 10:55:34.017 string[17634:303] 
array = (
 "",
 "",
 "",
 "\u8ba8\u538c\u7684\u8282\u70b9",
 "",
 "",
 "",
 "",
 "",
 "",
 "",
 "",
 ""
)
2016-01-17 10:55:34.049 string[17634:303] 
string = 讨厌的节点

2、带空格的字符串，如

@"hello world"去掉空格

nsstring *string2 = @"hello world";
 
/*处理空格*/
 
nscharacterset *characterset2 = [nscharacterset whitespacecharacterset];
 
// 将string1按characterset1中的元素分割成数组
nsarray *array2 = [string2 componentsseparatedbycharactersinset:characterset2];
 
nslog(@"\narray = %@",array2);
 
// 用来存放处理后的字符串
nsmutablestring *newstring1 = [nsmutablestring string];
 
for(nsstring *string in array1)
{
    [newstring1 appendstring:string];
}
nslog(@"newstring = %@", newstring1);

打印结果：

2016-01-17 11:02:49.656 string[17889:303] 
array = (
 hello,
 world
)
2016-01-17 11:02:49.657 string[17889:303] newstring = helloworld

ps：处理字母等其他元素只需将nscharacterset的值改变即可。

+ (id)controlcharacterset;
 
+ (id)whitespacecharacterset;
 
+ (id)whitespaceandnewlinecharacterset;
 
+ (id)decimaldigitcharacterset;
 
+ (id)lettercharacterset;
 
+ (id)lowercaselettercharacterset;
 
+ (id)uppercaselettercharacterset;
 
+ (id)nonbasecharacterset;
 
+ (id)alphanumericcharacterset;
 
+ (id)decomposablecharacterset;
 
+ (id)illegalcharacterset;
 
+ (id)punctuationcharacterset;
 
+ (id)capitalizedlettercharacterset;
 
+ (id)symbolcharacterset;
 
+ (id)newlinecharacterset ns_available(10_5, 2_0);
 
+ (id)charactersetwithrange:(nsrange)arange;
 
+ (id)charactersetwithcharactersinstring:(nsstring *)astring;
 
+ (id)charactersetwithbitmaprepresentation:(nsdata *)data;
 
+ (id)charactersetwithcontentsoffile:(nsstring *)fname;

二、用字符将nsarray中的元素拼接起来

nsarray *array = [nsarray arraywithobjects:@"hello",@"world",nil];
 
//如要用,:等字符串拼接，只需将下面的@" "空格换成@","或@":"即可
nsstring *string = [array componentsjoinedbystring:@" "];
 
nslog(@"string = %@",string);

打印结果：

hello world

三、截取子串：

这里以获取时间为例，利用nsdate获取到当前时间时，有时候只需要日期或者只需要时间

1、从字符串开头截取到指定的位置，如

//获取到当前日期时间   
nsdate *date = [nsdate date];
        
//定义日期格式,此处不重点讨论nsdate，故不详细说明，在后面会详细讨论      
nsdateformatter *dateformatter = [[nsdateformatter alloc] init];
        
//设置日期格式       
[dateformatter setdateformat:@"yyyy-mm-dd hh:mm"];
        
//将日期转换成nsstring类型     
nsstring *string = [dateformatter stringfromdate:date];
nslog(@"\ncurrent = %@",string);
               
//截取日期substringtoindex
nsstring *currentdate = [string substringtoindex:10];
                
nslog(@"\ncurrentdate = %@",currentdate);

打印结果：

current = 2016-01-1711:12


currentdate = 2016-01-17

2、抽取中间子串-substringwithrange

//截取月日
nsstring *currentmonthanddate = [string substringwithrange:[nsmakerange(5, 5)]];
        
nslog(@"currentmonthanddate = %@",currentmonthanddate);

打印结果：

currentmonthanddate = 06-27

3、从某一位置开始截取- substringfromindex

//截取时间substringfromindex
nsstring *currenttime = [string substringfromindex:11];
        
nslog(@"\ncurrenttime = %@",currenttime);\

打印结果：

currenttime = 11:25

四、比较字符串

nsstring *first = @"string";
nsstring *second = @"string";

1、判断两个字符串是否相同-isequaltostring方法

bool isequal = [first isequaltostring:second];
 
nslog(@"first is equal to second:%@",isequal);

打印结果：

first is equal to second:0

2、compare方法比较字符串三个值

nsorderedsame//是否相同
nsorderedascending//升序，按字母顺序比较，大于为真
nsordereddescending//降序，按字母顺序比较，小于为真

bool result = [first compare:sencond] == nsorderedsame;   
nslog(@"result:%d",result);

打印结果：

result:0 

bool result = [first compare:second] == nsorderedascending;   
nslog(@"result:%d",result);

打印结果：

result:0

bool result = [first compare:second] == nsordereddecending; nslog(@"result:%d",result);

打印结果：

result:1

3、不考虑大小写比较字符串

bool result = [first compare:second
                     options:nscaseinsensitivesearch | nsnumericsearch] == nsorderedsame;
nslog(@"result:%d",result);

打印结果：

result:1

五、改变字符串大小写

nsstring *astring = @"a string";
nsstring *string = @"string";
//大写
nslog(@"astring:%@",[astring uppercasestring]);
//小写
nslog(@"string:%@",[string lowercasestring]);
//首字母大小写
nslog(@"string:%@",[string capitalizedstring]);

打印结果：

astring:a string

string:string

string:string

六、在字符串中搜索子串

nsstring *string1 = @"this is a string";
nsstring *string2 = @"string";
nsrange range = [string1 rangeofstring:string2];
nsuinteger location = range.location;
nsuinteger leight = range.length;
nsstring *astring = [[nsstring alloc] initwithstring:[nsstring stringwithformat:@"location:%li,leight:%li",location,leight]];
nslog(@"astring:%@",astring);
[astring release];

打印结果：

astring:location:10,leight:6