Overlays: Difference between revisions
imported>Jtojnar Replace self/super with new convention final/prev |
imported>Tmillr m grammar |
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Here the main package set is extended with two overlays, ext-1 and ext-2. <tt>x // y</tt> is represented by a <tt>//</tt> box with <tt>x</tt> coming in from the left and <tt>y</tt> from above. | Here the main package set is extended with two overlays, ext-1 and ext-2. <tt>x // y</tt> is represented by a <tt>//</tt> box with <tt>x</tt> coming in from the left and <tt>y</tt> from above. | ||
As you can see, <tt>final</tt> is the same for every stage, but <tt>prev</tt> comes from only the stage before. So when you define an attribute <tt>foo</tt> in the set to override it, within that overlay <tt>final.foo</tt> will be | As you can see, <tt>final</tt> is the same for every stage, but <tt>prev</tt> comes from only the stage before. So when you define an attribute <tt>foo</tt> in the set to override it, within that overlay <tt>final.foo</tt> will be its version, and <tt>prev.foo</tt> will be the non-overriden version. This is why you see patterns like <tt>foo = prev.foo.override { ... }</tt>. | ||
The names <tt>final</tt> and <tt>prev</tt> might remind you of inheritance in object-oriented languages. In fact, overlays are exactly the same thing as subclasses, with regards to overriding and calling methods. This data flow is also how objects know which method to call. This is probably | The names <tt>final</tt> and <tt>prev</tt> might remind you of inheritance in object-oriented languages. In fact, overlays are exactly the same thing as subclasses, with regards to overriding and calling methods. This data flow is also how objects know which method to call. This is probably how the two arguments got their names, too. | ||
== Data flow of overlays (alternative explanation) == | == Data flow of overlays (alternative explanation) == | ||