How does XCGLogger interact with classes that implement both CustomStringConvertible and CustomDebugStringConvertible?

Question

I am trying out XCGLogger and noticed that if I have a logging statement that includes an object instance from a class that implements both CustomDebugStringConvertible and CustomStringConvertible the logger doesn't call the debugDescription property but only seems to invoke the description property from CustomStringConvertible.

My implementation of debugDescription contains additional information over the description property that I would like to be used in logging.

In this situation when both protocols are implemented is their a way to have the logger use debugDescription over description by default?

If only either CustomStringConvertible or CustomDebugStringConvertible is implemented does the logger detect this and use the implemented protocol?

Thanks

Answer 1

Using CustomStringConvertible or CustomDebugStringConvertible is something that happens before the string reaches XCGLogger. String interpolation will use the description property of CustomStringConvertible and not the debugDescription property of CustomDebugStringConvertible. debugDescription is only used when an object conforming to CustomDebugStringConvertible is passed to the debugPrint() method direction, not inside of quotes.

For example:

struct Sample: CustomStringConvertible, CustomDebugStringConvertible {
    var description: String { return "description" }
    var debugDescription: String { return "debugDescription" }
}

let sample = Sample()
print("\(sample)")          // description
debugPrint("\(sample)")     // "description"
print(sample)               // description
debugPrint(sample)          // debugDescription

A possible solution for you would be do add -DDEBUG to your Other Swift Flags (if not already there), and alter your description property to be something like this:

var description: String {
    #if DEBUG
        return debugDescription
    #else
        return "description"
    #endif
}

Then for debug builds, you'll get the debugDescription value used in string interpolation, but in your production builds, you'll get your normal description.

Answer 2

Adding onto Dave Wood's answer, when printing an Optional type, I've found that debugDescription will be prioritized over description

struct Sample: CustomStringConvertible, CustomDebugStringConvertible {
    var description: String { return "description" }
    var debugDescription: String { return "debugDescription" }
}

let n: Sample? = Sample()

print(n)                        // Optional(debugDescription)
debugPrint(n)                   // Optional(debugDescription)

print("\(n)")                   // Optional(debugDescription)
debugPrint("\(n)")              // "Optional(debugDescription)"

print(n!)                       // description
debugPrint(n!)                  // debugDescription

print("\(n!)")                  // description
debugPrint("\(n!)")             // "description"

print(String(describing: n))    // Optional(debugDescription)
print(String(reflecting: n))    // Optional(debugDescription)

print(String(describing: n!))   // description
print(String(reflecting: n!))   // debugDescription