In order to make integration of `cohortBuilder` package with other layers/packages easier, hooks system was introduced.
Many Cohort methods allow to define `hook` parameter. For such method, `hook` is a list containing two values: `pre` and `post`, storing functions (hooks) executed before and after the method is run respectively.
Each `hook` is a function of two obligatory parameters:
public Cohort object.
private Private environment of Cohort object.
When Cohort method, for which hook is defined, allow to pass custom parameters, the ones should be also available in hook definition (with some exclusions, see below).
For example `Cohort$remove_step` has three parameters:
By the implementation, the parameters that we should skip are `run_flow` and `hook`, so the hook should have three parameters `public`, `private` and `step_id`.
There are two ways of defining hooks for the specific method. The first one is to define the method `hook` directly as its parameter (while calling the method).
The second option can be achieved with usage of `add_hook` (and `get_hook`) function. The default `hook` parameter for each method is constructed as below:
remove_step = function(step_id, run_flow = FALSE, hook = list( pre = get_hook("pre_rm_step_hook"), post = get_hook("post_rm_step_hook") ) )
'Pre' hooks are defined with 'pre_<method_name>_hook' and 'Post' ones as 'post_<method_name>_hook'. As a result calling `add_hook("pre_remove_step_hook", function(public, private, step_id) ...)` will result with specifying a new pre-hook for `remove_step` method.
You may add as many hooks as you want. The order of hooks execution is followed by the order or registering process. If you want to check currently registered hooks for the specific method, just use: