Install a callback for the given event.
set_callback :save, :before, :before_meth set_callback :save, :after, :after_meth, if: :condition set_callback :save, :around, ->(r, &block) { stuff; result = block.call; stuff }
The second arguments indicates whether the callback is to be run
:before
, :after
, or :around
the
event. If omitted, :before
is assumed. This means the first
example above can also be written as:
set_callback :save, :before_meth
The callback can be specified as a symbol naming an instance method; as a
proc, lambda, or block; as a string to be instance evaluated; or as an
object that responds to a certain method determined by the
:scope
argument to define_callbacks
.
If a proc, lambda, or block is given, its body is evaluated in the context of the current object. It can also optionally accept the current object as an argument.
Before and around callbacks are called in the order that they are set; after callbacks are called in the reverse order.
Around callbacks can access the return value from the event, if it
wasn't halted, from the yield
call.
Options
-
:if
- A symbol naming an instance method or a proc; the callback will be called only when it returns atrue
value. -
:unless
- A symbol naming an instance method or a proc; the callback will be called only when it returns afalse
value. -
:prepend
- Iftrue
, the callback will be prepended to the existing chain rather than appended.
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