NSString与NSMutableString的基本使用

1.NSString

1.1创建方法 3种

NSString *str1 = [[NSString
alloc]init];

NSString *str2 =
@"Hello world";

NSString *str4 = [NSString
stringWithFormat:@"%@ words",@"hello"];

1.2截取方法 3种

NSString *str6 =
@"www.tedu.cn";

NSString *str7 = [str6 substringToIndex:3];//截取头

NSString *str8 = [str6 substringFromIndex:9];//截取尾

NSRange r = {4,4};
//NSRange是一个结构体

NSString *str9 = [str6 substringWithRange:r];//截取中断

1.3拼接方法 3种

NSString *str10 = @"Hello";

NSString *str11 = @"world";

NSString *str12 = [[NSString
alloc]initWithFormat:@"%@%@",str10,str11 ];//初始化拼接

        

NSString *str13 = [str10
stringByAppendingString:str11];//追加拼接

        

NSString *str14 = [str10
stringByAppendingFormat:@"%@,%d",str11,6];//格式化拼接（和追加拼接的区别：可以拼接数字）

1.4替换方法

NSString *str15 =
@"www.tarena.com.cn";

NSRange r1 = {4,10};

NSString *str16 = [str15
stringByReplacingCharactersInRange:r1
withString:@"tedu"];

1.5从文件中读入字符串

NSString *str17 = [NSString
stringWithContentsOfFile:@"/Users/tarena/Desktop/testString"
encoding:NSUTF8StringEncoding
error:nil];

2.NSMutableString

2.1是可变字符串，是NSString的子类

2.2创建(4种)

NSMutableString *str1 = [[NSMutableString
alloc]init];//空字符串，有意义

        

NSMutableString * str3 = [NSMutableString
stringWithCapacity:100];//100预估值，预先分配空间

        

NSMutableString *str4 = [NSMutab
a9ae
leString
stringWithString:@"string"];//标准方法

        

NSMutableString *str5 = [NSMutableString
stringWithFormat:@"age:%d",6];//标准格式化

2.3添加(2种)

[str3 appendString:@"the string"];//往空字符串添加,标准添加方法

[str3 appendString:@" has 6 characters."];

        

NSMutableString *str6 = [NSMutableString
stringWithString:@"the string"];

[str6 appendFormat:@" has %lu characters.",str6.length];//格式化添加

2.4求字符串中字符的个数

str6.length

2.5删除

NSMutableString *str7 = [NSMutableString
stringWithString:@"I am learning Objective-c language"];

NSRange r = [str7 rangeOfString:@"Objective-"];

[str7 deleteCharactersInRange:r];

2.6确定子串在整个字符串中的范围

rangeOfString:@"Objective-"

2.7替换

NSMutableString *str8 = [NSMutableString
stringWithString:@"This is a string"];

r = [str8 rangeOfString:@"a"];

[str8 replaceCharactersInRange:r
withString:@"another"];