Apple Guide FAQ | Controlling When Mixins Mix In

What is a mixin?
How do I decide whether to use mixins?
How do I set up and compile a mixin?
How do I control when a mixin mixes into the parent guide?
How do I use elements from the parent guide in a mixin?
Why does GuideMaker refuse to compile my mixin?
Why won't a mixin mix into the parent guide?
Why does the guide look strange when a mixin is active?

How do I control when a mixin mixes into the parent guide?

Three factors affect whether a mixin mixes in: the location of the mixin file, the qualifier resource (if any), and the <mixin match> code (if any):

A mixin must be in the same folder as the parent guide. If several mixins are in the same folder, they will all mix into every guide in that folder, unless you use the qualifier and <mixin match> mechanisms to prevent them from mixing into inappropriate parent guides.
If a mixin contains a qualifier resource, the mixin is blocked from mixing in if the qualifier returns false. A qualifier can test any part of the system's configuration, including hardware, system version, whether a particular file is present, and so forth.
If a mixin uses the <mixin match> command, it will only mix into parent guides that were compiled using the same <mixin match> signature. Likewise, parent guides with a <mixin match> can only be modified by mixins containing the same signature.

How do I use elements from the parent guide in a mixin?