不积跬步，无以至千里；不积小流，无以成江海.
NSString的创建
创建常量字符串,注意使用“@“符号
NSString *astring = @"This is a String!";
创建空字符串,给予赋值。
NSString *s = [[NSString alloc] init];
s=@"quanzi";
创建格式化字符串:占位符(由一个%加一个字符组成)
[NSString stringWithFormat:@"quanzi%i岁了", 30];
字符串比较
NSString *str1 = @"quanzi";
NSString *str2 =@"quanzi";
if (str1 == str2) {
NSLog(@"字符串地址一样");
}
if ([str1 isEqualToString:str2]) {
NSLog(@"字符串内容一样");
}
(NSComparisonResult)compare:(NSString *)string
- 这个方法可以用来比较两个字符串内容的大小
- 比较方法: 逐个字符地进行比较ASCII值，返回NSComparisonResult作为比较结果
- NSComparisonResult是一个枚举，有3个值:
- 如果左侧> 右侧,返回NSOrderedDescending,
- 如果左侧< 右侧,返回NSOrderedAscending,
- 如果左侧== 右侧返回NSOrderedSame
NSString *str1 = @"abc";
NSString *str2 = @"abd";
switch ([str1 compare:str2]) {
case NSOrderedAscending:
NSLog(@"后面一个字符串大于前面一个");
break;
case NSOrderedDescending:
NSLog(@"后面一个字符串小于前面一个");
break;
case NSOrderedSame:
NSLog(@"两个字符串一样");
break;
}
输出结果: 后面一个字符串大于前面一个
(NSComparisonResult) caseInsensitiveCompare:(NSString *)string;
- 忽略大小写进行比较，返回值与compare:一致
NSString *str1 = @"abc";
NSString *str2 = @"ABC";
switch ([str1 caseInsensitiveCompare:str2]) {
case NSOrderedAscending:
NSLog(@"后面一个字符串大于前面一个");
break;
case NSOrderedDescending:
NSLog(@"后面一个字符串小于前面一个");
break;
case NSOrderedSame:
NSLog(@"两个字符串一样");
break;
}
输出结果:两个字符串一样
字符串搜索
(BOOL)hasPrefix:(NSString *)aString;
是否以aString开头
NSString *str1 = @"abcdef";
NSString *str2 =@"ab";
bool b = [str1 hasPrefix:str2];
NSLog(@"%i",b);
(BOOL)hasSuffix:(NSString *)aString;
是否以aString结尾
NSString *str3=@"ef";
bool b2 = [str1 hasSuffix:str3];
NSLog(@"%i",b2);
(NSRange)rangeOfString:(NSString *)aString;
1.用来检查字符串内容中是否包含了aString
2.如果包含, 就返回aString的范围
3.如果不包含, NSRange的location为NSNotFound, length为0
NSRange r = [str1 rangeOfString:str2];
NSLog(@"长度是=%i,位置是=%i",r.length,r.location);//长度是=2,位置是=0
字符串截取
(NSString *)substringFromIndex:(NSUInteger)from;
从指定位置from开始(包括指定位置的字符)到尾部
NSString *str1 = @"fakjhfakjnfjahfj";
str1 = [str1 substringFromIndex:7];
NSLog(@"str = %@", str1); //kjnfjahfj
(NSString *)substringToIndex:(NSUInteger)to;
从字符串的开头一直截取到指定的位置to，但不包括该位置的字符
NSString *str2 = @"fakjhfakjnfjahfj";
str2 = [str2 substringToIndex:10];
NSLog(@"str = %@", str2); //fakjhfakjn
(NSString *)substringWithRange:(NSRange)range;
按照所给出的NSRange从字符串中截取子串
NSString *str = @"<head>quanzi</head>";
NSRange range;
range.location = [str rangeOfString:@">"].location + 1;
range.length = [str rangeOfString:@"</"].location - range.location;
NSString *res = [str substringWithRange:range];
NSLog(@"res = %@", res);//quanzi
字符串替换
(NSString)stringByReplacingOccurrencesOfString:(NSString )target withString:(NSString *)replacement;
用replacement替换target
NSString *str1 = @"http:**quanzi.com*img*info";
NSString *newStr1 = [str1 stringByReplacingOccurrencesOfString:@"*" withString:@"/"];
NSLog(@"newStr = %@", newStr1);//newStr1 = http://quanzi.com/img/info
(NSString )stringByTrimmingCharactersInSet:(NSCharacterSet )set;
去除首尾
NSString *str2 = @" http://quanzi.com/img/info ";
NSString *newStr2 = [str2 stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
NSLog(@"newStr =|%@|", newStr2);//newStr2 =|http://quanzi.com/img/info|
NSString *str3 = @"***http://quanzi.com/img/info***";
NSString *newStr3 = [str3 stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"*"]];
NSLog(@"newStr =%@", newStr3);//newStr =http://quanzi.com/img/info
字符串转换
转为基本数据类型
(double)doubleValue;
(float)floatValue;
(int)intValue;
NSString *str1 = @"110";
NSString *str2 = @"10";
int res = str1.intValue + str2.intValue;
NSLog(@"res = %i", res); //120
NSString *str1 = @"110";
NSString *str2 = @"10.1";
double res = str1.doubleValue + str2.doubleValue;
NSLog(@"res = %f", res);//120.100000
转为C语言中的字符串
(char *)UTF8String;
NSString *str = @"abc";
const char *cStr = [str UTF8String];
NSLog(@"cStr = %s", cStr);//cStr = abc
char *cStr = "abc";
NSString *str = [NSString stringWithUTF8String:cStr];
NSLog(@"str = %@", str);//str = abc
字符串大小写转换
全部字符转为大写字母
(NSString *)uppercaseString;
NSString *str = @"abc";
str = [str uppercaseString];
NSLog(@"str = %@", str);//str = ABC
全部字符转为小写字母
(NSString *)lowercaseString
NSString *str = @"ABC";
str = [str lowercaseString];
NSLog(@"str = %@", str);//str = abc
首字母变大写，其他字母都变小写
(NSString *)capitalizedString
NSString *str = @"abdcfaDFJdfjh";
str = [str capitalizedString];
NSLog(@"str = %@", str);//str = Abdcfadfjdfjh
字符串路径的判断
(BOOL)isAbsolutePath;
是否为绝对路径
//其实就是判断是否以/开头//
NSString *str = @"Users/quanzi/Desktop/info.txt";//不是绝对路径
if ([str isAbsolutePath]) {
NSLog(@"是绝对路径");
}else
{
NSLog(@"不是绝对路径");
}
(NSString *)lastPathComponent;
获得最后一个目录
// 截取最后一个/后面的内容
NSString *str = @"/Users/quanzi/Desktop/info.txt";
NSString *component = [str lastPathComponent];
NSLog(@"component = %@", component);//info.txt
(NSString *)stringByDeletingLastPathComponent;
删除最后一个目录
// 其实就是上次最后一个/和之后的内容
NSString *str = @"/Users/quanzi/Desktop/info.txt";
NSString *newStr = [str stringByDeletingLastPathComponent];
NSLog(@"newStr = %@", newStr);///Users/quanzi/Desktop
(NSString )stringByAppendingPathComponent:(NSString )str;
在路径的后面拼接一个目录 (也可以使用stringByAppendingString:或者stringByAppendingFormat:拼接字符串内容)
// 其实就是在最后面加上/和要拼接得内容
// 注意会判断后面有没有/有就不添加了, 没有就添加, 并且如果有多个会替换为1个
NSString *str = @"/Users/quanzi/Desktop/";
NSString *newStr = [str stringByAppendingPathComponent:@"info.txt"];
NSLog(@"newStr = %@", newStr);///Users/quanzi/Desktop/info.txt
(NSString *)pathExtension;
获得拓展名
// 其实就是从最后面开始截取.之后的内容
NSString *str = @"info.txt";
NSString *str = @"abc.info.txt";
NSString *extension = [str pathExtension];
NSLog(@"extension = %@", extension);//extension = txt
(NSString *)stringByDeletingPathExtension;
删除尾部的拓展名
NSString *str = @"abc.info.txt";
NSString *newStr = [str stringByDeletingPathExtension];
NSLog(@"newStr = %@", newStr);//newStr = abc.lnj
(NSString )stringByAppendingPathExtension:(NSString )str;
在尾部添加一个拓展名
// 其实就是在最后面拼接上.和指定的内容
NSString *str = @"info";
NSString *newStr = [str stringByAppendingPathExtension:@"gif"];
NSLog(@"newStr = %@", newStr);//newStr = info.gif
本文都是个人的一部分总结,以后都会不断的更新和总结.有什么写的不对的地方,欢迎大神指导.
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