Orange!

--> Note this is a work in progess... In fact some things described here are how things are supposed to work but some features are unimplemented.

Orange is a data binding language you can use in your iOS projects--you can replace your controller code with it. It's also good for writing layout code.

The basic construct in Orange is a bind statement. It looks like this:

object.keypath <= expression

This means "when the result of expression changes, assign it to the location at object.keypath.

You can put bind statements inside a scope. This allows you to bind multiple key paths of a single object:

object.long.key.path {
    .bottom <= 10.0;
    .top <= 0.0;
}

You can nest scopes:

view { .backgroundColor { .red <= 0.5; .green <= 0.2; .blue < 1.0 } }

Note that the bind statements inside a scope don't need to specify the target object--it is specified by the key path in the parent scope. At the top level of your script the parent scope is the object the script is attached to. The keyword self represents "the object to script is attached to".

Normally bindings are always ‘live’. Changes in the expression are applied at the destination keypath immediately. You can specify a trigger as a scope and this causes your bindings to run only at certain times. For example, you can use the trigger "layout" to run your bindings during -layoutSubviews:

<layout> {
    .subviews {
    .left <= 10.0;
    .right <= 100.0;
    }
}

Compile your scripts like this:

[ OrangeScript scriptWithContext:myObject format:@".height <= 20" ] ;

You can refer to object instances in Orange script by passing them as additional arguments to the compiler:

[ OrangeScript scriptWithContext:myObject format:@".title <= %@.title", titleContainer ] ;

This works like printf... Use the %@ specifier.

Expressions

Expressions are written in prefix notation.

Examples:

addition

+ 5 10

subtraction (take 5 from 10)

- 10 5

ternary (if/then/else) operator:

#
# if a.hidden then result is 0
# otherwise result is a.width
#

? a.hidden 0 a.width

you can also optionally group subexpressions using parentheses:

#
# add 15 to (10 - 7)
#

+ ( - 10 7 ) 15

you can message objects just like in Obj-C:

[ UIImage imageNamed:"test.png" ]