In Rails 5 you have to throw :abort otherwise it won’t work. (even returning false) Also, you should add prepend: true to the callback, to make sure it runs before the dependent: :destroy on the parent models. Something like this should work: class Something < ApplicationRecord before_destroy :can_destroy?, prepend: true private def can_destroy? if model.something? … Read more
There are many valid ways to callback into Java from C/C++. I’m going to show you a technique using C (easy to adjust env for C++) that makes it fairly easy to pass data from native code to Java code. This example passes strings ( easy to modify for any data type ). In native … Read more
I strongly prefer the first way for several reasons: Representing concepts/functionality via interfaces/class hierarchies makes the code base less generic, flexible, and then more difficult to mantain or scale in the future. That kind of design imposes a set of requirements on the type (the type implementing the required functionality) which makes it difficult to … Read more
You can call Model._save_callbacks to get a list of all callbacks on save. You can then filter it down to what kind you need e.g. :before or :after like this: Model._save_callbacks.select {|cb| cb.kind == :before} Works the same for Model._destroy_callbacks etc.
done is a method called internally by the strategy implementation. Then it navigates you, as you can see, to one of the success / error / fail methods (again, by the implementation. there are more options). Each of these options may calls to the next, where in your snippet code is the following: function(req, res) … Read more
.complete + callback This is a standards compliant method without extra dependencies, and waits no longer than necessary: var img = document.querySelector(‘img’) function loaded() { alert(‘loaded’) } if (img.complete) { loaded() } else { img.addEventListener(‘load’, loaded) img.addEventListener(‘error’, function() { alert(‘error’) }) } Source: http://www.html5rocks.com/en/tutorials/es6/promises/
Using ‘&?’ returns undefined if the attribute has not been set. ‘&’ = callback function is defined always. ‘&?’ = callback function is defined only when attribute is defined in html template. bindToController: { callback: ‘&?’ }, controller: function() { if (this.callback === undefined) { // attribute “callback” was not defined } } Note: Works … Read more
From the Meteor.call documentation: On the client, if you do not pass a callback and you are not inside a stub, call will return undefined, and you will have no way to get the return value of the method. That is because the client doesn’t have fibers, so there is not actually any way it … Read more
This is a more general answer for future viewers. Callback types There are a few different types of predefined callbacks: final VoidCallback myVoidCallback = () {}; final ValueGetter<int> myValueGetter = () => 42; final ValueSetter<int> myValueSetter = (value) {}; final ValueChanged<int> myValueSetter = (value) {}; Notes: VoidCallback is an anonymous function that takes no arguments … Read more
Edit 2014-01-28: New readers, make sure you check out Zac’s answer below. He has a much neater solution that will let you define and instantiate a scoped function in the class definition using the fat arrow syntax. The only thing I will add is that, in regard to option 5 in Zac’s answer, it’s possible … Read more