Abstract methods means there is no default implementation for it and an implementing class will provide the details. Essentially, you would have abstract class AbstractObject { public abstract void method(); } class ImplementingObject extends AbstractObject { public void method() { doSomething(); } } So, it’s exactly as the error states: your abstract method can not … Read more
Extending a bit Alexey’s perfect answer : Dispatch::all() => Returns a Collection Dispatch::all()->where() => Returns a Collection Dispatch::where() => Returns a Query Dispatch::where()->get() => Returns a Collection Dispatch::where()->get()->where() => Returns a Collection You can only invoke “paginate” on a Query, not on a Collection. And yes, it is totally confusing to have a where function … Read more
Yes, it is possible, when your constructor function executes, the this value has already the [[Prototype]] internal property pointing to the ValidateFields.prototype object. Now, by looking at the your edit, the errArray variable is not available in the scope of the CreateErrorList method, since it is bound only to the scope of the constructor itself. … Read more
A benefit of this is that it allows you to take an instance method and turn it into a static method without having to modify any existing code (other than the class) and thus allowing for backwards compatibility. I’ve found this useful as many times I’ve come across utility methods that can be made static … Read more
Before Rust 1.33, there are only four valid method receivers: struct Foo; impl Foo { fn by_val(self: Foo) {} // a.k.a. by_val(self) fn by_ref(self: &Foo) {} // a.k.a. by_ref(&self) fn by_mut_ref(self: &mut Foo) {} // a.k.a. by_mut_ref(&mut self) fn by_box(self: Box<Foo>) {} // no short form } fn main() {} Originally, Rust didn’t have this … Read more
The source is often helpful: http://kickjava.com/src/java/util/HashMap.java.htm remove: O(1) size: O(1) values: O(n) (on traversal through iterator)
It depends on how the attribute itself is declared – see AttributeUsageAttribute.Inherited property.
In fact the difference between adding methods dynamically at run time and your example is huge: in your case, you just attach a function to an object, you can call it of course but it is unbound, it has no relation with the object itself (ie. you cannot use self inside the function) when added … Read more
If AnInterface is Java, it can work with SAM conversion: val impl = AnInterface { inst, num -> //… } Otherwise, if the interface is Kotlin: Since Kotlin 1.4, it’s possible to write functional interfaces : fun interface AnInterface { fun doSmth(inst: MyClass, num: Int) } val impl = AnInterface { inst, num -> … … Read more
You created a Blog model. Once you migrate this, Django will create a table with “name” and “tagline” columns in your database. If you want to interact with the database with the model, for example create an instance of the model and save it or retrieve the model from db, def __str__(self): return self.name will … Read more