This code helps you find strings nested into hierarchies of NSDictionary and NSArray

FindStringDeepInDictionary.m

// Usage:
// NSString *toFind = @"theString";
// NSString *result = [self findStringInDictionary:dict searchString:toFind];


-(NSString *)findStringInDictionary:(NSMutableDictionary *)dict searchString:(NSString *)searchString {
    NSString __block *toReturn = nil;
    [dict enumerateKeysAndObjectsUsingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
        if ([obj isKindOfClass:[NSString class]]) {
            
            if ([obj rangeOfString:searchString].location == 0) {
            
            toReturn = key;
                *stop = YES;
            }
        } else if ([obj isKindOfClass:[NSArray class]]) {
            toReturn = [self findStringInArray:obj searchString:searchString];
            if (toReturn != nil) { *stop = YES; }
        } else if ([obj isKindOfClass:[NSDictionary class]]) {
            toReturn = [self findStringInDictionary:obj searchString:searchString];
            if (toReturn != nil) { *stop = YES; }
        }
        
    }];
    
    return toReturn;
}

-(NSString *)findStringInArray:(NSMutableArray *)array searchString:(NSString *)searchString {
    
    NSString __block *toReturn = nil;

    [array enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        if ([obj isKindOfClass:[NSString class]]) {
            if ([obj rangeOfString:searchString].location == 0) {
                
                toReturn = obj;
                *stop = YES;

            }
            
        } else if ([obj isKindOfClass:[NSArray class]]) {
            toReturn = [self findStringInArray:obj searchString:searchString];
            if (toReturn != nil) { *stop = YES; }
        } else if ([obj isKindOfClass:[NSDictionary class]]) {
            toReturn = [self findStringInDictionary:obj searchString:searchString];
            if (toReturn != nil) { *stop = YES; }
        }
    }];
    
    return toReturn;

}