[self.indexArray sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
return [obj1 compare:obj2];
NSString *str1 = obj1;
NSString *str2 = obj2;
if (str1 > str2) {
returnNSOrderedAscending;
}else if(str1 < str2){
returnNSOrderedDescending;
}returnNSOrderedSame;
}];