polymorphism

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;

问题 I'm sorry i couldn't find a better title. I'm trying to achieve something like the following abstract class Person case class User(uid: String, firstname: String, active: String) extends Person case class Admin(id: String, pseudo: String, securityClearance: String) extends Person def innerFunctionForUser(user: User): List[String] = { List() :+ user.uid :+ user.firstname :+ user.active } def innerFunctionForAdmin(admin: Admin): List[String] = { List() :+ admin.id :+ admin.psuedo :+ admin

问题 I have the following code for a tree structure: class Node: def __init__(self, node_id: str): self.node_id = node_id self.children = [] def add_child(self, node: 'Node'): if isinstance(node, Node): self.children.append(node) class ValueNode(Node): def __init__(self, value: bool, **kwargs): Node.__init__(self, **kwargs) self.value = value class LogicNode(Node): def __init__(self, logic_operator: str, **kwargs): Node.__init__(self, **kwargs) self.logic_operator = logic_operator a = Node("a") b

问题 I know that (Int) -> Void can't be typecasted to (Any) -> Void : let intHandler: (Int) -> Void = { i in print(i) } var anyHandler: (Any) -> Void = intHandler <<<< ERROR This gives: error: cannot convert value of type '(Int) -> Void' to specified type '(Any) -> Void' Question : But I don't know why this work? let intResolver: ((Int) -> Void) -> Void = { f in f(5) } let stringResolver: ((String) -> Void) -> Void = { f in f("wth") } var anyResolver: ((Any) -> Void) -> Void = intResolver I messed

问题 In the Laravel documentation, there is the following example for retrieving morphedByMany relations, which are many-to-many polymorphic relations. Laravel Many to Many polymorphic relations documentation namespace App; use Illuminate\Database\Eloquent\Model; class Tag extends Model { /** * Get all of the posts that are assigned this tag. */ public function posts() { return $this->morphedByMany('App\Post', 'taggable'); } /** * Get all of the videos that are assigned this tag. */ public

问题 In the Laravel documentation, there is the following example for retrieving morphedByMany relations, which are many-to-many polymorphic relations. Laravel Many to Many polymorphic relations documentation namespace App; use Illuminate\Database\Eloquent\Model; class Tag extends Model { /** * Get all of the posts that are assigned this tag. */ public function posts() { return $this->morphedByMany('App\Post', 'taggable'); } /** * Get all of the videos that are assigned this tag. */ public

问题 I am having an F# exam in 10 days and as I am currently doing old exam sets, I ran into a problem understanding generics and especially types that have two polymorphic arguments. The questions should be rather easy to solve, but how it works syntactically, I am not sure. The old exam question is as follows: The following type Sum<'a,'b> comprises two different kinds of values type Sum<'a,'b> = | Left of 'a | Right of 'b Now I need to write two values of type Sum<int list, bool option> , one

问题 I am having an F# exam in 10 days and as I am currently doing old exam sets, I ran into a problem understanding generics and especially types that have two polymorphic arguments. The questions should be rather easy to solve, but how it works syntactically, I am not sure. The old exam question is as follows: The following type Sum<'a,'b> comprises two different kinds of values type Sum<'a,'b> = | Left of 'a | Right of 'b Now I need to write two values of type Sum<int list, bool option> , one

问题 I am having an F# exam in 10 days and as I am currently doing old exam sets, I ran into a problem understanding generics and especially types that have two polymorphic arguments. The questions should be rather easy to solve, but how it works syntactically, I am not sure. The old exam question is as follows: The following type Sum<'a,'b> comprises two different kinds of values type Sum<'a,'b> = | Left of 'a | Right of 'b Now I need to write two values of type Sum<int list, bool option> , one