iOS开发Extra系列:NSString***
在iOS系统,NSString可能是最常用的对象,很多用法跟其他语言不一样。
##字符串对象NSString
###使用格式创建字符串
+ (id)stringWithFormat:(NSString *)format...
- (id)initWithFormat:(NSString *)format...
NSString *str = "hello";
NSString *string = [NSString stringWithFormat:@"%@ world",str];
NSLog(string); 结果:hello world
###常用的替换符
%@ NSString实例
%d,%D,%i 整数
%4d,%4D,%4i 格式化整数
%ld,%lD,%li 长整数
%u,%U 无符号整数
%x 将无符号整数以十六进制小写字母显示
%X 将无符号整数以十六进制大写字母显示
%f 小数
%c 字符
%s C语言字符串
%% 显示%字符本身
##范围集合NSRange
###定义
typedef struct _NSRange
{
unsigned int location;
unsigned int length;
}NSRange;
###NSMakeRange函数
这个函数比较特殊 返回一个NSRange的对象。
NSMakeRanger(unsigned int location,unsigned int length);
例如:
NSRange range = NSMakeRanger(0,5);
NSLog(@"location is %d,length is %d",range.location,range.length);
###查找
如果找到就返回范围,否则NSRange的location项被设置为NSNotFound
- (NSRange)rangeOfString:(NSString *)subString;
- (NSRange)rangeOfString:(NSString *)subString option:(unsigned)mask;
- (NSRange)rangeOfString:(NSString *)subString option:(unsigned)mask range:(NSRange)range;
//mask常用选项列表
//NSCaseInsensitiveSearch 不区分字母大小写
//NSLiteralSearch 对字符串进行字节单位的比较,一般可提高检索速度
//NSBackwardsSearch 从范围的末尾开始检索
//NSAnchoredSearch 仅检索制定范围的前部。忽略字符串中间的检索字符
NSString *string = @"hello world";
NSRange range = [string rangeOfString:@"he"];
if(range.location != NSNotFound)
{
NSLog(@" location=%d,length=%d",range.location,range.length);
}
###截取字符串
NSString
//返回字符串开头至index位的字符串 不包含索引位
- (NSString *)substringToIndex:(unsigned)index;
//返回字符串第index位至末尾的字符串 包含索引位
- (NSString *)substringFromIndex:(unsigned)index;
//返回字符串中范围range内的字符串
- (NSString *)substringWithRange:(NSRange)range;
//包含索引位
NSString *string = [string substringWithRange:NSMakeRange(5,2)];
###比较字符串
NSString *String1 = @"NSStringInformation.txt";
//hasPrefix 前缀比较
[String1 hasPrefix:@"NSString"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");
//hasSuffix 后缀比较
[String1 hasSuffix:@".txt"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");
//isEqualToString 完全比较
if([string1 isEqualToString:@""])
{
NSLog(@"string1 is blank");
}
###替换字符串
NSString *newString = [oldString stringByReplacingOccurrencesOfString:@"x" withString:@"y"];
###分离字符串成数组
NSString *string = @"A|B|C|D";
NSArray *array = [string componentsSeparatedByString:@"|"];
###读取文本文件
NSString
+ (id)stringWithContentsOfFile:(NSString *)path usedEncoding:(NSStringEncoding *)enc error:(NSError **)error //自动释放内存
- (id)initWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error
NSString *string = [NSString stringWithContentsOfFile:@"/user/test/yw.txt" encoding:NSUTF8StringEncoding error:&error];
if(string){}
###输出文本文件
NSString
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile encoding:(NSStringEncoding)enc error:(NSError **)error
//参数 atomically 暂时将文件保存到辅助文件中
//path
The file to which to write the receiver. If path contains a tilde (~) character, you must expand it withstringByExpandingTildeInPath before invoking this method.
//扩展路径
NSString *Path = @"~/NSData.txt";
NSString *absolutePath = [Path stringByExpandingTildeInPath];
NSLog(@"absolutePath:%@",absolutePath);
NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);
//文件扩展名
NSString *Path = @"~/NSData.txt";
NSLog(@"Extension:%@",[Path pathExtension]);