iPhone之NSString常用方法介绍

今天我们介绍iPhone开发的NSString与NSMutableString的常用方法。NSString 的 Class Reference 非常庞大，请参考官方文档：

https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html

NSString一直使用，但总没有好好整理它的用法。NSString与int，float等类型的转换见：

http://blog.youkuaiyun.com/htttw/article/details/7842955

直接上代码，注释很详细，不多说了：

-(void)testNSString
{
	//初始化 NSString
	NSString * str1 = [[NSString alloc] init];
	str1 = @"This is NSString1";
	NSLog(@"str1: %@", str1);
	//NSString字符串的的长度
	NSLog(@"str1的长度: %d", [str1 length]);
	[str1 release];
	
	//也可以用下面的方法初始化 NSString
	NSString * str2 = [[NSString alloc] initWithString:@"This is NSString2"];
	NSLog(@"str2: %@", str2);
	[str2 release];
	
	//也可以用char *创建 NSString字符串
	char * chr = "This is NSString3";
	NSString * str3 = [[NSString alloc] initWithCString:chr];
	NSLog(@"str3: %@", str3);
	[str3 release];
	
	//创建格式化字符串
	int a1 = 1, a2 = 2;
	NSString * str4 = [[NSString alloc] initWithString:[NSString stringWithFormat:@"a1= %d, a2 = %d", a1, a2]];
	NSLog(@"str4: %@", str4);
	[str4 release];
	
	
	//创建临时字符串（不用手动释放）
	NSString * str6 = [NSString stringWithString:@"This is a temporary string2"];
	NSLog(@"str6: %@", str6);
	
	
	//注意: 在电脑的根目录下创建! 并不是在模拟器或iPhone真机上创建!
	NSString * path = @"test.txt";
	//NSString 与文件操作
	//写文件
	NSString * str7 = [[NSString alloc] initWithString:@"哈哈 This string is written to a file"];
	NSString * str7_2 = [[NSString alloc] initWithCString:"哈哈 This string is written to a file" encoding:NSUTF8StringEncoding];

	
	[str7 writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:nil];
	NSLog(@"str7: %@", str7);
	
	[str7 release];
	
	[str7_2 writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:nil];
	NSLog(@"str7_2: %@", str7_2);
	[str7_2 release];
	

	//读文件
	NSString * str8 = [[NSString alloc] initWithContentsOfFile:path];
	NSLog(@"str8: %@", str8);
	[str8 release];
	
	NSString * str8_2 = [[NSString alloc] initWithContentsOfFile:path];
	NSLog(@"str8_2: %@", str8_2);
	[str8_2 release];
	
	
	
	//char *用strcmp比较
	char * chr1 = "char1";
	char * chr2 = "char2";
	if(strcmp(chr1, chr2) == 0)
	{
		NSLog(@"chr1 等于 chr2");
	}
	else
	{
		NSLog(@"chr1 不等于 chr2");
	}

	
	//NSString *用isEqualToString比较（相等返回YES，否则返回NO）
	NSString * str9  = @"String9";
	NSString * str10 = @"String10";
	NSString * str11 = @"String9";
	NSLog(@"str9 isEqualToString:str10: %d", [str9 isEqualToString:str10]);
	NSLog(@"str9 isEqualToString:str11: %d", [str9 isEqualToString:str11]);

	//compare方法(comparer返回的三种值)
	NSLog(@"NSOrderedSame = %d", NSOrderedSame);
	NSLog(@"NSOrderedAscending = %d", NSOrderedAscending);
	NSLog(@"NSOrderedDescending = %d", NSOrderedDescending);

	NSString * str12 = @"String";
	NSString * str13 = @"String";
	//NSOrderedSame: 判断两者是否相同
	NSLog(@"[str12 compare:str13]: %d", [str12 compare:str13]);

	
	NSString * str14 = @"String";
	NSString * str15 = @"string";
	NSString * str16 = @"sting";
	//逐字符按ASCII码比较
	//简记为:
	//如果NSOrderedSame，则前后相等
	//如果NSOrderedAscending，则前小后大
	//如果NSOrderedDescending，则前大后小
	if([str14 compare:str15] == NSOrderedAscending)
	{
		NSLog(@"str14 小于 str15");
	}
	else
	{
		NSLog(@"str14 大于 str15");
	}
	
	if([str15 compare:str16] == NSOrderedDescending)
	{
		NSLog(@"str15 大于 str16");
	}
	else
	{
		NSLog(@"str15 小于 str16");
	}
	
	//不考虑大小写比较
	if([str14 caseInsensitiveCompare:str15] == NSOrderedSame)
	{
		NSLog(@"不区分大小写: str14 等于 str15");
	}
	else
	{
		NSLog(@"不区分大小写: str14 不等于 str15");
	}
	
	
	//NSString拼接
	NSString * str17 = @"str17";
	NSString * str18 = @"str18";
	//方法1（推荐）
	NSString * str19 = [str17 stringByAppendingString:str18];
	NSLog(str19, nil);
	//方法2
	NSString * str20 = [NSString stringWithFormat:@"%@%@", str17, str18];
	NSLog(str20, nil);
	//方法3
	NSString * str21 = [@"" stringByAppendingFormat:@"%@%@", str17, str18];
	NSLog(str21, nil);
	//方法4
	NSMutableString * ms = [[NSMutableString alloc] init];
	[ms appendString:str17];
	[ms appendString:str18];
	NSLog(ms, nil);
	[ms release];
	
	//去除头尾空格
	NSString * str22 = @"   I have white space   ";
	NSString * str23 = [str22 stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
	NSLog(@"str22: %@", str22);
	NSLog(@"str23: %@", str23);
	
	
	//换行
	NSString * str24 = @"\n I am in the first line.\n I am in the second line.";
	NSLog(str24, nil);
	
	//换行写可以提高可读性
	NSString * str25 = @"SELECT [CustomerID], [CustomerName] "
						"FROM [Customer] "
						"WHERE [CustomerID] = 1234";
	
	NSString * str26 = @"SELECT [CustomerID], [CustomerName] \
FROM [Customer] \
WHERE [CustomerID] = 1234";
	//str25 和 str26是一样的
	NSLog(str25, nil);
	NSLog(str26, nil);
	
	
	//NSMutableString
	NSMutableString * str27 = [NSMutableString stringWithString:@"hello world"]; 
	NSLog(str27, nil);
	
	//生成空字符串
	NSMutableString * str28 = [NSMutableString string]; 
	[str28 appendString:@"hello"]; 
	[str28 appendString:@" world"]; 
	NSLog(@"str28 = %@", str28);
	
	//插入字符串
	NSMutableString * str29 = [NSMutableString stringWithString:@"Mac X"]; 
	//在第4个字符处(从0开始算)插入
	[str29 insertString:@"OS " atIndex:4]; 
	NSLog(@"str29 = %@", str29);
	
	//删除字符串
	NSMutableString * str30 = [NSMutableString stringWithString:@"Mac OS X"]; 
	//deleteCharactersInRange:NSMakeRange(start, length): 从第start个字符开始，删除length个
	[str30 deleteCharactersInRange:NSMakeRange(2, 3)]; 
	NSLog(@"str30 = %@", str30);
	
	//前缀和后缀
	NSString * str31 = @"Mac OS"; 
	NSString * str32 = @"Mac Pro";
	//前缀
	if([str31 hasPrefix:@"Ma"])
	{
		NSLog(@"Has prefix: Ma");
	}
	else
	{
		NSLog(@"Don't have prefix: Ma");
	}	
	//后缀
	if([str32 hasSuffix:@"c Pro"])
	{
		NSLog(@"Has suffix: c Pro");
	}
	else
	{
		NSLog(@"Don't have suffix: c Pro");
	}
	
	//字符串检索
	NSString * str33 = @"Hello World! Welcome to Mac OS X";
	//返回找到的第一个的 NSRange
	NSRange range1 = [str33 rangeOfString:@"el"]; 
	if(range1.location == NSNotFound) 
	{
		NSLog(@" \'el\' not found in \'%@\'", str33);
	}
	else
	{
		NSLog(@" Found: location = %d, length = %d", range1.location, range1.length); 
	} 
	

	//不区分大小写搜索
	NSRange range2 = [str33 rangeOfString:@"m" options:NSCaseInsensitiveSearch]; 
	//从后往前搜索(如果找到，则返回的值仍是正方向数的序号)
	NSRange range3 = [str33 rangeOfString:@"m" options:NSBackwardsSearch]; 

	if(range2.location == NSNotFound) 
	{
		NSLog(@"不区分大小写: \'m\' not found in \'%@\'", str33);
	}
	else
	{
		NSLog(@"不区分大小写: Found: location = %d, length = %d", range2.location, range2.length); 
	} 
	
	if(range3.location == NSNotFound) 
	{
		NSLog(@"从后往前: \'m\' not found in \'%@\'", str33);
	}
	else
	{
		NSLog(@"从后往前: Found: location = %d, length = %d", range3.location, range3.length); 
	} 
	
	//截取字符串
	//返回字符串开头至index位的字符串, 不包含索引位 
	NSString * str34 = [str33 substringToIndex:8];
	//返回字符串第index位至末尾的字符串, 包含索引位 
	NSString * str35 = [str33 substringFromIndex:15];
	//返回字符串中范围range内的字符串, 包含索引位. 即:
	//substringWithRange:NSMakeRange(start, length): 返回从第start个字符开始的length个字符
	NSString * str36 = [str33 substringWithRange:NSMakeRange(3, 15)];
						
	NSLog(@"str34 = %@", str34);
	NSLog(@"str35 = %@", str35);
	NSLog(@"str36 = %@", str36);
}