Object-C 字符串

Object-C 字符串

NSString 不可变字符串

1.快速初始化

NSString *string1 = @"sadfadsf";

2.格式化的方式初始化字符串

NSString *string5 = @"linlin";        NSString *string6 = @"666";        NSString *string7 = [NSString stringWithFormat:@"%@%@",string5,string6];        NSLog(@"string7 = %@",string7);

note:对于用格式化方式来构造字符串实例来讲，其作用并不是仅仅来构造一个字符串对象，它还可以用来做字符串拼接

3.从本地文件中读取字符串

        NSString *path = @"/Users/Desktop/        OC/OC_06_02/OC_06_02/t.html";        NSError *error ;        NSStringEncoding encoding ;        NSString *string8 =         [NSString stringWithContentsOfFile:path         encoding:NSUTF8StringEncoding error:&error];        NSString *string9 =         [NSString stringWithContentsOfFile:path         usedEncoding:&encoding error:&error];//        NSLog(@"string8 = %@,error = %@",string8,error);        NSLog(@"string9 = %@ ,encoding =         %lu",string9,encoding);

4.从网络中读取一个字符串

NSURL *url = [NSURL URLWithString:@"http://www.baidu.com"];        NSString *string10 = [NSString stringWithContentsOfURL:url encoding:4 error:&error];        NSLog(@"stirng10 = %@",string10);

字符串的操作

1.字符串长度

NSUInteger length = string11.length ;

2.字符串的截取

NSString *subStr1 = [string11 substringToIndex:8];        NSLog(@"subStr1 = %@",subStr1);        NSString *subStr2 = [string11 substringFromIndex:8];        NSLog(@"subStr2 = %@",subStr2);        NSString *subStr3 = [string11 substringWithRange:NSMakeRange(8, length -8)];        NSLog(@"subStr3 = %@",subStr3);

3.字符串比较
‘==’：表示两个字符串内容和指针都相等

[subStr2 isEqualToString:subStr3]：表示两个字符串内容是否相同

 if ([subStr2 isEqualToString:subStr3])        {            NSLog(@"subStr2 和 subStr3 相等");        }        else        {            NSLog(@"subStr2 和 subStr3 不相等");        }

4.根据字符串拿到对应的range

 NSRange range = [string11 rangeOfString:@"斗非架"];        NSLog(@"range = %@",[NSValue valueWithRange:range]);        NSRange range1 = [string11 rangeOfString:@"非"];        NSLog(@"rang1 = %@",[NSValue valueWithRange:range1]);

5.判断字符串是否由xx前缀或xx后缀

 NSString *string12 = @"http://www.baidu.com";        if ([string12 hasPrefix:@"http://"])        {            NSLog(@"含有此前缀");        }        else        {            NSLog(@"不含有此前缀");        }        NSString *string13 = @"sdsddfs.jpg";        if ([string13 hasSuffix:@".jpg"]||[string13 hasSuffix:@".png"])        {            NSLog(@"含有此后缀");        }

6.字符串拼接

NSString *string15 = [@"http://" stringByAppendingString:string12];        NSLog(@"%@",string15);        NSString *domainStr = @"http://www.baidu.com";        NSString *xxx = @"login";        NSString *string16 = [NSString stringWithFormat:@"%@/%@",domainStr,xxx];        NSLog(@"%@",string16);        NSString *string17 = [domainStr stringByAppendingPathComponent:xxx];        NSLog(@"%@",string17);        //http://pic.nipic.com/2007-11-09/2007119122519868_2.jpg        NSString *imagePath = @"http://pic.nipic.com/2007-11-09/2007119122519868_2.jpg";        imagePath = [imagePath lastPathComponent];        NSLog(@"%@",imagePath);        NSString *theImageName = @"linlin";        theImageName = [theImageName  stringByAppendingPathExtension:@"png"];        NSLog(@"%@",theImageName);