Why rex_text for UILabel returns not optional string

[Igor-Palaguta]

Hello,

UILabel has var text: String?

Why rex_text does not have MutableProperty<String?> type?
currently have to write in many places label.rex_text <~ optionalText.map { $0 ?? "" }

Thanks!

[Rui Peres]

Good point, we would need to make a new major release for this change tho. 😕

[Neil Pankey]

We're still on 0.x releases so we can safely change this in 0.x+1 and be semver compliant.

[Yannick Compernol]

I'm not a fan of this change, even when ignoring the compilation errors I now get everywhere, this feels like a step backwards away from the "Swift way".

I found the type being a non optional String a feature rather than a bug. When setting the text property there's no difference between nil or an empty String, both have the same result, being an empty UILabel. Hence MutableProperty<String> simplified the use. Now, when testing whether a UILabel is empty, we have to test whether the value is nil and whether it's an empty String.

Logically, an empty UILabel contains an empty String, the nil situation is/was an old Objective-C side-effect. Imho.

For instance a ViewModel exposes a username property of type MutableProperty<String>, this used to match with rex_text without having to add map's everywhere and manually handling the nil situation.

Update 8/1/16: Changed UITextField to UILabel which I had mixed up. Issue was about UILabel to start with.

[Rui Peres]

@ynnckcmprnl we have tried to be coherent with what the different APIs expose and respect it. In this particular case, having a new look at it, I kinda agree with you. @dmcrodrigues what do you think?

[David Rodrigues]

@ynnckcmprnl thanks for your feedback and I agree in reverting this. To ground this decision there's a discussion in the documentation that clearly states:

This string is @"" by default.

I also have done a few tests and even when you clear a text field with a nil value you always receive an empty string while accessing text property.

@ynnckcmprnl are you interested in contributing this change?

[David Rodrigues]

Note however that UILabel, which was the issue stated here, should remain an optional string because it's nil by default as we can see in the documentation.

[Yannick Compernol]

Darn, I seem to have mixed up UILabel & UITextField. My issue was indeed with UILabel though, the post should have said UILabel instead of UITextField. I'll update the post to prevent further confusion.

I still stand by my original opinion, but the documentation stating nil as default value does make it a hard sell.

Good catch regarding UITextField, the change to MutableProperty<String> should be inarguable.

[David Rodrigues]

@ynnckcmprnl I don't think we should change this for UILabel, the documentation clearly states that by default it's nil so it's not case where the API exposed is not coherent but a case where we are making an assumption.

One thing we can do to help with this change is cherry-picking the support for binding with optionals.

struct ViewModel {
    let name: MutableProperty<String>
}

// This will be possible without any mapping
nameLabel.rex_text <~ viewModel.name

This will help? @RuiAAPeres what do you think about this?

[Yannick Compernol]

@dmcrodrigues That would be exactly what I need.

[David Rodrigues]

I wish that was included in RAC 4.x but unfortunately it will become available only in RAC5. Until then, I think we can provide it through Rex but I'll ask the opinion of @neilpa and @RuiAAPeres about this.

[Rui Peres]

@ynnckcmprnl kinda wasted effort to add this to Rex and just remove it again later on. It might be preferable to add this on your own codebase as a small extension and remove it, once you adopt RAC5.