1. Application Specific Information:
   *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSCFString rangeOfString:options:range:locale:]: nil argument'

solution：
情形一：str 不能為nil， 需進(jìn)行判空處理，否則當(dāng)str == nil，是就會crash, 注意containsString 是iOS8中才出現(xiàn)的API，所以在小于iOS8的系統(tǒng)中運(yùn)行也將導(dǎo)致程序崩潰

NSString method "containsString:" 

/// str must not be nil. 
-(BOOL)containsString:(NSString *)str;

情形二：searchString 不能為nil， 需進(jìn)行判空處理，否則當(dāng)searchString == nil，是就會crash,

NSString method "rangeOfString:" 

/// searchString must not be nil. 
- (NSRange)rangeOfString:(NSString *)searchString;