refactor: Update NSDictionary+CaseInsensitive to Swift

[BrandonStalnaker]

Summary

• Port NSDictionary(MPCaseInsensitive) to Swift

Testing Plan

• ran in sample app and confirmed all unit tests

Reference Issue (For mParticle employees only. Ignore if you are an outside contributor)

• Closes https://go.mparticle.com/work/SQDSDKS-6985

[einsteinx2]

I see that the MPKitContainerTests testForwardAppsFlyerEvent test is failing on this branch due to these changes. I checked out the development branch and confirmed it passes there.

Once that test is fixed and new dedicated tests added for these methods, I can re-review and make any final suggestions to simplify the implementation.

[einsteinx2]

This will crash any time element.key is not a String. Since this is inside a reduce closure, you can use a guard let statement here and it will return from the closure, not the whole function.

Something like this should work:

Suggested change

	let key = element.key as! String
	guard let key = element.key as? String else { return }

[einsteinx2]

Same here

Suggested change

	let key = element.key as! String
	guard let key = element.key as? String else { return }

[einsteinx2]

This has slightly different behavior than the original Obj-C code. In the original, it stops searching after finding the correct key, but in this code it will continue. It's not possible to use break here as it it's an actual for loop, and if you use return it will return from the closure, but I believe it will continue to loop. Instead this can be written as a for in loop:

Suggested change

	var localKey = key
	self.allKeys.forEach { keyValue in
	if let stringKey = keyValue as? String, stringKey.caseInsensitiveCompare(key) == .orderedSame {
	localKey = stringKey
	}
	}
	return localKey
	for aKey in allKeys {
	if let stringKey = aKey as? String, stringKey.caseInsensitiveCompare(key) == .orderedSame {
	return stringKey
	}
	}
	return key

[einsteinx2]

Same here. Also caqn be slightly simplified since with a for in loop you can get the key and value directly:

Suggested change

	var value : Any?
	self.allKeys.forEach { keyValue in
	if let stringKey = keyValue as? String, stringKey.caseInsensitiveCompare(key) == .orderedSame {
	value = self[stringKey]
	}
	}
	return value
	for (aKey, value) in self {
	if let stringKey = aKey as? String, stringKey.caseInsensitiveCompare(key) == .orderedSame {
	return value
	}
	}
	return nil

[einsteinx2]

This method really needs a dedicate unit test written in Objective-C that passes in a dictionary of all of the supported types from all the ifs and confirms the output strings. First make sure it passes against the original Obj-C implementation then against this one.

[einsteinx2]

Double check that the use of the reduce method here doesn't bridge the NSDictionary to a Swift dict and mess up some of the types... The added unit test should catch that though.

[einsteinx2]

Once the tests are fixed and new tests added, this can probably be simplified so that you only write the implementations for NSDictionary or Swift dictionary and then cast to the other type. That way you don't need to duplicate the implementations.

For sure it can be done for the caseInsensitiveKey and value(forCaseInsensitiveKey key: String) methods, but transformValuesToString may have issues due to bridging messing up the types, though it would probably still be fine if the Swift implementation cases to NSDictionary vs the other way around.