How to compare two UIDynamicProviderColor?

问题

I'm comparing two UIColor initialised using the new iOS 13 init(dynamicProvider:)

https://developer.apple.com/documentation/uikit/uicolor/3238041-init

but that's what I get runtime when I compare them in unit test with an XCTAssertEqual:

XCTAssertEqual failed: ("Optional(<UIDynamicProviderColor: {...}; 
provider = <__NSMallocBlock__: {...}>>)") is not equal to 
("Optional(<UIDynamicProviderColor: {...}; provider = <__NSMallocBlock__: {...}>>)")

This is an example of how I create the color:

struct Style {
    static var color: UIColor {
        if #available(iOS 13.0, *) {
                return UIColor { traitCollection in
                    return traitCollection.userInterfaceStyle == .dark ? .secondarySystemBackground : UIColor.white
                }
        } else {
            return UIColor.white
        }
    }
}

The test code:

func testExample() {
    XCTAssertEqual(Style.color, Style.color)
}

I tried overriding isEqual method of UIColor with an extension but apparently it's not called.

Do you have any workaround for this?

回答1:

One solution to your unit test is by changing your code to this:

XCTAssertEqual(Style.color.cgColor, yourExpectedColor.cgColor)

In the iOS 13 at runtime it is comparing two UIDynamicProviderColor objects that return an UIColor object after running a block "(UITraitCollection) -> UIColor". So, that's the reason you have two different objects. Getting the cgColor from both you can compare them correctly. I hope I was helpfull.

回答2:

Currently we do the following:

func equals(_ object: Any?) -> Bool {
    guard let rhs = object as? UIColor else { return false }

    var lhsR: CGFloat = 0
    var lhsG: CGFloat = 0
    var lhsB: CGFloat = 0
    var lhsA: CGFloat = 0
    getRed(&lhsR, green: &lhsG, blue: &lhsB, alpha: &lhsA)

    var rhsR: CGFloat = 0
    var rhsG: CGFloat = 0
    var rhsB: CGFloat = 0
    var rhsA: CGFloat = 0
    rhs.getRed(&rhsR, green: &rhsG, blue: &rhsB, alpha: &rhsA)

    return  lhsR == rhsR && lhsG == rhsG && lhsB == rhsB && lhsA == rhsA
}

With this in place you cannot use == anymore but have to explicitly call this function when you want to compare colors.

But a much better solution would have to compare each representation of the color by using resolvedColor(with:). But this would have to be implemented by Apple so we can continue using == nad the Equatable protocol.

来源：https://stackoverflow.com/questions/58065340/how-to-compare-two-uidynamicprovidercolor

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swift

ios13