IOS笔记之字符串

1.C语言到Object的转换

char *s = "Hello";
//OC、C字符窜类型转换
//C->OC
NSString * str1 = [NSString stringWithUTF8String:s] ;
NSLog(@"str1=%@",str1);
//OC->C
NSLog(@"str2 = %s",[str1 UTF8String]);

2.创建字符串

NSString *str3 = @"ios";
NSString *str4 =[[NSString alloc] init]; //需要手动释放内存
str4 = @"IOS";

3.格式化字符串

int a = 10;
int b =20;
NSString *str5 =[NSString stringWithFormat:@"a= %d,b=%d",a,b];
NSLog(@"str5=%@",str5);

4.拼接字符串

NSString *str6 = [str5 stringByAppendingString:str1];
NSLog(@"str6= %@",str6);

5.大小写转换

//转化小写
NSString *str7 = @"ABCDEF";
NSString *str8 = [str7 lowercaseString];
NSLog(@"str8 = %@",str8);

//转化大写
NSString *str9 = [str7 uppercaseString];
NSLog(@"str9=%@",str9);

6.前缀和后缀的判断

//判断前缀
NSString *str10 = @"www.imooc.com";
BOOL hasPreFix = [str10 hasPrefix:@"www."];
if(hasPreFix){
    NSLog(@"有对应前缀");
}else{
    NSLog(@"没有对应前缀");
}

//判断后缀
BOOL hasSuffix = [str10 hasSuffix:@".com"];
if(hasSuffix){
    NSLog(@"有对应后缀");
}else{
    NSLog(@"有对应后缀");
}

7.判断两个字符窜是否相同

NSString *str11 = @"hello world";
NSString *str12 = @"hello";
if([str11 isEqualToString:str12]){
    NSLog(@"两个字符窜一致");
}else{
    NSLog(@"两个字符窜不一致");
}

8.分割字符串

//按照指定字符分割字符串
NSString *str13 = @"a,b,c,d,e,f,g";
NSArray *strArray = [str13 componentsSeparatedByString:@","];
for (NSString *s in strArray) {
    NSLog(@"s =%@",s);
}

//按照范围截取字符串
NSRange range = NSMakeRange(1, 5); //包含头尾
NSString *str14 = [str13 substringWithRange:range];
NSLog(@"str14= %@",str14);

//从某一位开始截取后面字符串
NSString *str15 = [str13 substringFromIndex:2];
NSLog(@"str15 = %@",str15);

//从开头截取到某一位
NSString *str16 = [str13 substringToIndex:7];
NSLog(@"str16 =%@",str16);

//将字符串拆分为每一个字符
for (int i =0; i < str13.length; i++) {
    NSLog(@"%c",[str13 characterAtIndex:i]);
}

9.查找字符窜

NSString *str17 = @"ab cd ef gh ij ab";
NSRange range1 = [str17 rangeOfString:@"ab"];
NSLog(@"location:%ld,length:%ld",range1.location,range1.length);

10.替换字符串

//用指定字符串替换原字符窜
NSString *str20 = [str18 
stringByReplacingOccurrencesOfString:@"Hello" withString:@"你好"];
NSLog(@"str20 =%@",str20);

11.获取文件

文件来源：1.本地文件。2.网络文件

本地文件读取：
NSString *fileStr = [NSString stringWithContentsOfFile:@"/Users/xxx/Desktop/test.txt" encoding:NSUTF8StringEncoding error:nil];
NSLog(@"fileStr =%@",fileStr);

本地文件写入:
NSString *str22 = @"hello wuxuanyi";
BOOL isOK = [str22 writeToFile:@"/Users/xxx/Desktop/wuxuanyi.txt" atomically:YES encoding:NSUTF8StringEncoding error:nil];
if(isOK){
    NSLog(@"写入文件成功");
}else{
    NSLog(@"写入文件失败");
}

网络文件读取：
NSURL *httpURL = [NSURL URLWithString:str21]; //网络路径
NSString *httpStr = [NSString 
stringWithContentsOfURL:httpURL encoding:NSUTF8StringEncoding error:nil];
        NSLog(@"httpStr= %@",httpStr);