Make Parsing Methods Type Safe

[ankit-thanekar007]

PrebidSDK Expects Passthrough as an Array on auction response. But it's possible for it to come in as a dictionary from Prebid Server.

Consider this as an example

    NSMutableDictionary *jsonDictionary = [NSMutableDictionary new];
    
    jsonDictionary[@"passthrough"] = @{@"Test1" : @"Passthrough", @"Test2" : @"Crash"};
    
    NSArray<PBMJsonDictionary*> * const passthroughDics = jsonDictionary[@"passthrough"];

    if (passthroughDics) {
        for(PBMJsonDictionary *nextDic in passthroughDics) {
            if ([nextDic isKindOfClass:[NSString class]]) {
                NSLog(@"is String");
            }else if ([nextDic isKindOfClass:[NSArray class]]) {
                NSLog(@"is Array");
            }else if ([nextDic isKindOfClass:[PBMJsonDictionary class]]) {
                NSLog(@"is PBMJsonDictionary");
            }
        }
    }

Here jsonDictionary[@"passthrough"]; is coming in as a dictionary.

When this line executes
NSArray<PBMJsonDictionary*> * const passthroughDics = jsonDictionary[@"passthrough"];
it sets passthroughDics as a NSDictionary

Due to which nextDic in for(PBMJsonDictionary *nextDic in passthroughDics) { is set as NSString

The next line in PrebidSDK is

PBMORTBExtPrebidPassthrough * const nextPassthrough = [[PBMORTBExtPrebidPassthrough alloc] initWithJsonDictionary:nextDic];

which calls init for PBMORTBExtPrebidPassthrough where it executes this line _type = jsonDictionary[@"type"];

This line tries to subscript type inside a NSString which leads to this crash

-[__NSCFString objectForKeyedSubscript:]: unrecognized selector sent to instance 0x300dad3b0

Approach --> We make sure to check for the expected class before accessing or initializing the objects.

[ankit-thanekar007]

@jsligh @YuriyVelichkoPI