Declarative layout specifications about reactivecocoalayout

[dannygreg]

I would love to see a similar ASCII API. It is by far one of the (only? ) good things about AL.

[jspahrsummers]

It occurs to me that declarative layouts could perhaps be done with macros too. For example, the above specification could maybe be expressed as something like:

H(8, firstView, 20, secondView, 8)

There's some readability lost, but, in exchange, we'd get:

1. Compile-time expression validity checks. An invalid expression won't compile. (Of course, there are still ways to specify logically invalid layouts that fail at runtime.)
2. No messy view or metrics dictionaries. All values would be literals, or direct variable/constant references.

[jspahrsummers]

So, one of the big problems with the ideas so far (and AL's ASCII art too) is that you can only specify layouts in one direction at a time. I'd be interested in any ideas people have to incorporate both dimensions somehow.

[alanjrogers]

I've always wanted to be able to do something like this in AL, visual format:

@"H:|-(8)-[firstView]-(20)-[secondView]-(8)-|, V:|[firstView]|, V:|[secondView]"

Not sure how that would translate into a macro though.

[jspahrsummers]

I don't think that really solves the 2D problem, not least because it's not any more readable than doing that same thing over a few lines.

Essentially, using RCL, a view's complete frame should be specified from the signal that it's bound to. You shouldn't bind the X and Y axes separately. Although it might work, it would result in a lot of overhead as the property mutates twice for most triggers.

[alanjrogers]

Ah understood. In that case, then we could look at having a 2D ASCII art representation, but that's also going to be hard to do in a macro.

[zakdances]

I'm doing something similar with my iOS animation manager library Anim. I'm using a declarative ASCII like approach that uses NSArrays instead of strings to sequence stuff. You can drop in simple NSNumber literals like @2.3 for delays.

[jspahrsummers]

rentzsch/AutoLayoutShorthand might be good to look at while doing this.

It also occurred to me that nested macros (like EXTADT) could accomplish a lot of this with some additional static verification.