NSString

1.初始化

1. char *str1="C string";//这是C语言创建的字符串

2. NSString *str2=@"OC string";//ObjC字符串需要加@,并且这种方式创建的对象不需要自己释 放内存

3. //下面的创建方法都应该释放内存

4. NSString *str3=[[NSString alloc] init];

5. str3=@"OC string";


6.  

7. NSString *str4=[[NSString alloc] initWithString:@"Objective-C string"];


8.  

9. NSString *str5=[[NSString alloc] initWithFormat:@"age is %i,name is%.2f",19,1.72f];


10.  

11. NSString *str6=[[NSString alloc] initWithUTF8String:"C string"];//C语言的字符串转换为ObjC字符串


12.  

13. //以上方法都有对应静态方法(一般以string开头),不需要管理内存(系统静态方法一般都是自动 释放)

14. NSString *str7=[NSString stringWithString:@"Objective-C string"];

2.字符串的大小写和比较

1. NSLog(@""Hello world!" to upper is %@",[@"Hello world!" uppercaseString]); //结果:"Hello world!" to upper is HELLO WORLD!


2.  

3. NSLog(@""Hello world!" to lowwer is %@",[@"Hello world!" lowercaseString]); //结果:"Hello world!" to lowwer is hello world!


4.  

5. //首字母大写,其他字母小写

6. NSLog(@""Hello world!" to capitalize is %@",[@"Hello world!" capitalizedString]);

7. //结果:"Hello world!" to capitalize is Hello World!


8.  

9. BOOL result= [@"abc" isEqualToString:@"aBc"];

10. NSLog(@"%i",result);

11. //结果:0


12.  

13. NSComparisonResult result2= [@"abc" compare:@"aBc"];//如果是[@"abc"caseInsensitiveCompare:@"aBc"]则忽略大小写比较

14. if(result2==NSOrderedAscending){//-1实际上是枚举值

15.        NSLog(@"left<right.");

16. }else if(result2==NSOrderedDescending){//1

17.        NSLog(@"left>right.");

18. }else if(result2==NSOrderedSame){//0

19.        NSLog(@"left=right."); }

20.        //结果:left>right.

21. }

3.截取和匹配

NSLog(@"has prefix ab? %i",[@"abcdef" hasPrefix:@"ab"]);

//结果:has prefix ab? 1   YES 头部匹配

       

NSLog(@"has suffix ab? %i",[@"abcdef" hasSuffix:@"ef"]);

//结果:has suffix ab? 1   NO  尾巴匹配

       

NSRange range=[@"abcdefabcdef" rangeOfString:@"cde"];//注意如果遇到cde则不再往后面搜索,如果从后面搜索或其他搜索方式可以设置第二个options参数

if(range.location==NSNotFound){

     NSLog(@"not found.");

}

else{

     NSLog(@"range is %@",NSStringFromRange(range));

}

//结果:range is {2, 3}

4.字符串的分割

NSLog(@"%@",[@"abcdef" substringFromIndex:3]);

//结果:def //从index＝3开始直到末尾，包含index＝3

       

NSLog(@"%@",[@"abcdef" substringToIndex:3]);

//结果:abc //从index＝0开始直到index＝3，但是不包含index＝3

       

NSLog(@"%@",[@"abcdef" substringWithRange:NSMakeRange(2, 3)]);

//结果:cde

       

NSString *str1=@"12.abcd.3a";

NSArray *array1=[str1 componentsSeparatedByString:@"."];

//字符串分割

NSLog(@"%@",array1);


//

(
   12,
   abcd,
   3a
)

5.其他

NSLog(@"%i",[@"12" intValue]);//类型转换

//结果:12

       

NSLog(@"%zi",[@"hello world,世界你好!" length]);//字符串长度注意不是字节数

//结果:17

       

NSLog(@"%c",[@"abc" characterAtIndex:0]);//取出制定位置的字符

//结果:a

       

const char *s=[@"abc" UTF8String];//转换为C语言字符串

NSLog(@"%s",s);

//结果:abc