NSString

字符串的创建

NSString *s1 = @"jack";

NSString *s2 = [[NSString alloc] initWithString:@"jack"];

NSString *s3 = [[NSString alloc] initWithFormat:@"age is %d", 10];

C字符串 > C字符串

const char *c = [s4 UTF8String];

NSUTF8StringEncoding 用到中文就可以用这种编码

NSString *s5 = [[NSString alloc] initWithContentsOfFile:@"/Users/apple/Desktop/1.txt" encoding:NSUTF8StringEncoding error:nil];

字符串的导出

NSString *str = @"4234234";

NSURL *url = [NSURL fileURLWithPath:@"/Users/apple/Desktop/my2.txt"];

[str writeToURL:url atomically:YES encoding:NSUTF8StringEncoding error:nil];

或者

[@"Jack\nJack" writeToFile:@"/Users/apple/Desktop/my.txt" atomically:YES encoding:NSUTF8StringEncoding error:nil]

NSMutableString

可变字符串

NSMutableString *s1 = [NSMutableString stringWithFormat:@"my age is 10"];

拼接内容到s1的后面

[s1 appendString:@" 11 12"];

获取is的范围

NSRange range = [s1 rangeOfString:@"is"];

删除is

[s1 deleteCharactersInRange:range];

不可变字符串也可以将两个字符串拼接    

NSString *s2 = [NSString stringWithFormat:@"age is 10"];

NSString *s3 = [s2 stringByAppendingString:@" 11 12"];

补充知识：NSURL

 file://   本地资源协议头

 http://   网络资源协议头

创建一个资源路径

NSURL *url = [[NSURL alloc] initWithString:@"file:///Users/apple/Desktop/1.txt"]  本地资源

NSURL *url = [NSURL fileURLWithPath:@"/Users/apple/Desktop/1.txt"]  本地资源

将资源路径转化为字符串

NSString *s6 = [[NSString alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil] 

黑马程序员___Foundation__NSString