traits

I have a trait. For the sake of creativity, let's call this trait Trait: trait Trait{ static function treat($instance){ // treat that trait instance with care } } Now, I also have a class that uses this trait, User. When trying to call treat with an instance of User, everything works. But I would like to type-hint that only instances of classes using Trait should be given as arguments, like that: static function treat(Trait $instance){...} Sadly, though, this results in a fatal error that says the function was expecting an instance of Trait, but an instance of User was given. That type of type

I want to to extend a trait within a trait, like this: trait NodeTypes { trait Node { def allNodesHaveThis: Int } } trait ScrumptiousTypes extends NodeTypes { trait Node extends super.Node { def scrumptiousness: Int } } trait YummyTypes extends NodeTypes { trait Node extends super.Node { def yumminess: Int } } object Graph extends NodeTypes with ScrumptiousTypes with YummyTypes { case class Node() extends super.Node { override def allNodesHaveThis = 1 override def scrumptiousness = 2 // error: ScrumptiousTypes.Node has been disinherited override def yumminess = 3 } } If this works, it would be

Consider the following toy example: use std::cmp::Ordering; pub trait SimpleOrder { fn key(&self) -> u32; } impl PartialOrd for dyn SimpleOrder { fn partial_cmp(&self, other: &dyn SimpleOrder) -> Option<Ordering> { Some(self.cmp(other)) } } impl Ord for dyn SimpleOrder { fn cmp(&self, other: &dyn SimpleOrder) -> Ordering { self.key().cmp(&other.key()) } } impl PartialEq for dyn SimpleOrder { fn eq(&self, other: &dyn SimpleOrder) -> bool { self.key() == other.key() } } impl Eq for SimpleOrder {} This doesn't compile. It claims there is a lifetime issue in the implementation for partial_cmp :

I'd like to know if there is any way to prevent the use of trait methods out of any class context in PHP ? Let me explain what I want with a short example, here is my current code : // File : MyFunctions.php trait MyFunctions { function hello_world() { echo 'Hello World !'; } } // File : A.php include 'MyFunctions.php'; class A { use MyFunctions; } // File : testTraits.php include 'A.php'; hello_world(); // Call to undefined function -> OK, expected A::hello_world(); // Hello World ! -> OK, expected MyFunctions::hello_world(); // Hello World ! -> Maybe OK, but not expected, I'd like to prevent

Are there any contradictions to use traits to inject helper methods like this? class Foo { use Helper\Array; function isFooValid(array $foo) { return $this->arrayContainsOnly('BarClass', $foo); } } That's the idea with traits. However you should still keep an eye out for coupled code. If Helper\Array is a completely different namespace from what Foo is in you might want to re-think this particular approach. Traits have been added to PHP for a very simple reason: PHP does not support multiple inheritance. Simply put, a class cannot extends more than on class at a time. This becomes laborious

I was just reading about traits and how multiple php traits can be used in the same php code separated by commas. I do not however understand the concept of the insteadof keyword that is used to resolve conflict in case two traits have the same function. Can anyone please explain how insteadof keyword works and how to use it to tell the engine that I am willing to use function hello() of trait A instead of that of trait B, given there are two traits A and B and a function hello() in both the traits. Explanation According to Traits Documentation , when you have same method in multiple trait,

This question already has answers here : Possible Duplicate: traits in php – any real world examples/best practices? In what kind of situations would one use Traits in PHP? I do have a pretty good overall idea of this, but I can't seem to think of a way to use them in an application I have written, but that may be because it does not need traits at the time. One scenario I have realized that needs traits: Events. Instead of having one class that implements the observer pattern and letting all other classes inheriting it, just make it a trait and let classes that want to fire events or