//是否以str開(kāi)頭
- (BOOL)hasPrefix:(NSString*)str;
//是否以str結(jié)束
- (BOOL)hasSuffix:(NSString*)str;
//是否包含某字符串
- (NSRange)rangeOfString:(NSString*)searchString;
//是否包含某字符串(副加查找條件)
- (NSRange)rangeOfString:(NSString*)searchString options:(NSStringCompareOptions)mask;
typedefNS_OPTIONS(NSUInteger, NSStringCompareOptions)?
{
NSCaseInsensitiveSearch = 1,//不區(qū)分大小寫(xiě)比較
NSLiteralSearch = 2,//逐字節(jié)比較區(qū)分大小寫(xiě)
NSBackwardsSearch = 4,//從字符串末尾開(kāi)始搜索
NSAnchoredSearch = 8,//搜索限制范圍的字符串
NSNumericSearch = 64,//按照字符串里的數(shù)字為依據(jù)肮雨，算出順序箱玷。例如 Foo2.txt < Foo7.txt < Foo25.txt
NSDiacriticInsensitiveSearchNS_ENUM_AVAILABLE(10_5, 2_0) = 128,//忽略 "-" 符號(hào)的比較
NSWidthInsensitiveSearchNS_ENUM_AVAILABLE(10_5, 2_0) = 256,//忽略字符串的長(zhǎng)度陌宿，比較出結(jié)果
NSForcedOrderingSearchNS_ENUM_AVAILABLE(10_5, 2_0) = 512,//忽略不區(qū)分大小寫(xiě)比較的選項(xiàng)波丰，并強(qiáng)制返回 NSOrderedAscending 或者 NSOrderedDescending
NSRegularExpressionSearchNS_ENUM_AVAILABLE(10_7, 3_2) = 1024//只能應(yīng)用于 rangeOfString:..., stringByReplacingOccurrencesOfString:...和 replaceOccurrencesOfString:... 方法掰烟。使用通用兼容的比較方法，如果設(shè)置此項(xiàng)媚赖，可以去掉 NSCaseInsensitiveSearch 和 NSAnchoredSearch
};
//替換字符串
- (NSString*)stringByReplacingOccurrencesOfString:(NSString*)target withString:(NSString*)replacement;
//某一位置上的字符
- (unichar)characterAtIndex:(NSUInteger)index;
