Reimplement interception by using swizzling instead of URLProtocol
akashivskyy opened this issue · comments
Using a custom URLProtocol
subclass to intercept HTTP(S) traffic surely results in being a good citizen, but, as a way to debug apps, it comes with disadvantages:
-
First of all, the architecture of
URLProtocol
requires the subclasses to operate on static levels, essentially making them singletons. This has an implication that only one interception mechanism can exist at a time, even when using multipleURLSession
s. -
Using
URLProtocol
that internally uses anotherURLSession
prevents users of ResponseDetective from using their customURLSession
subclasses or evenURLSessionDelegate
s. SinceURLProtocol
doesn't have access to the custom delegates, issues line #2 emerge.
The alternative to using a custom URLProtocol
is to use swizzling to create a trampoline of URLSessionDelegate
that would have the following advantages:
-
There can be multiple instances of interceptors, one per each
URLSession
instance. This makes them more configurable and even more testable. This resolves the first problem ofURLProtocol
. -
Since the trampoline of
URLSessionDelegate
would bounce back to the "original" delegate set by user, users will still be able to customize the behavior ofURLSession
directly (even by subclassing it). This resolves the second problem ofURLProtocol
and #2. -
Swizzling doesn't require users to pass custom
URLSessionConfiguration
s toURLSession
s during initialization, which enables them to inject ResponseDetective at any time to any existing instance ofURLSession
. -
Swizzling can optionally be done globally during application launch, which would enable users to inject ResponseDetective to
URLSession
instances they do not own. This would enable them to debug traffic in third-party dependencies.
As seen above, using swizzling may eventually be a better, more customizable and safer implementation of ResponseDetective.
+1 for this one. Especially useful for 3rd party debugging, but also other traffic, not necessarily owned by app, like AVPlayer. FLEX debugger can be probably used as a reference, from what I've seen, swizzling is used there.