Difference
Better way to identify what's different between 2 instances.
Have you ever written tests?
Usually they use equality asserts, e.g. XCTAssertEqual, what happens if the objects aren't equal? Xcode throws a wall of text at you:
This forces you to manually scan the text and try to figure out exactly what's wrong, what if instead you could just learn which property is different?
Installation
CocoaPods
Add pod 'Difference' to your Podfile.
Carthage
Add github "krzysztofzablocki/Difference" to your Cartfile.
SwiftPM
Add .package(name: "Difference", url: "https://github.com/krzysztofzablocki/Difference.git", .branch("master")), dependency in your Package manifest.
Using lldb
Write the following to see the difference between 2 instances:
po dumpDiff(expected, received)
Integrate with XCTest
Add this to your test target:
public func XCTAssertEqual<T: Equatable>(_ expected: @autoclosure () throws -> T, _ received: @autoclosure () throws -> T, file: StaticString = #filePath, line: UInt = #line) {
do {
let expected = try expected()
let received = try received()
XCTAssertTrue(expected == received, "Found difference for \n" + diff(expected, received).joined(separator: ", "), file: file, line: line)
}
catch {
XCTFail("Caught error while testing: \(error)", file: file, line: line)
}
}Replace #filePath with #file if you're using Xcode 11 or earlier.
Integrate with Quick
Add this to your test target:
public func equalDiff<T: Equatable>(_ expectedValue: T?) -> Predicate<T> {
return Predicate.define { actualExpression in
let receivedValue = try actualExpression.evaluate()
if receivedValue == nil {
var message = ExpectationMessage.fail("")
if let expectedValue = expectedValue {
message = ExpectationMessage.expectedCustomValueTo("equal <\(expectedValue)>", actual: "nil")
}
return PredicateResult(status: .fail, message: message)
}
if expectedValue == nil {
return PredicateResult(status: .fail, message: ExpectationMessage.fail("").appendedBeNilHint())
}
return PredicateResult(bool: receivedValue == expectedValue, message: ExpectationMessage.fail("Found difference for " + diff(expectedValue, receivedValue).joined(separator: ", ")))
}
}Write the following to see the difference between 2 instances:
expect(received).to(equalDiff(expected))
Integrate with The Composable Architecture
If you are using The Composable Architecture nameLabels configuration to get a diff that's more appropiate for reducer instrumentation
diff(oldState, newState, indentationType: .pipe, nameLabels: .comparing)You can use this function in your own variant of ReducerInstrumentation code based on this
That way your diffs will look more like this:
Received action:
AppAction.home(.howTo(.setSelectedSlide))
State:
home:
| selectedHowTo:
| | selectedSlide:
| | | Current: 8mnkni91h4fe
| | | Previous: exei4wpqsmdk