this

js call static method from class

微笑、不失礼 提交于 2019-11-27 15:59:54
I have a class with a static method: class User { constructor() { User.staticMethod(); } static staticMethod() {} } Is there something like this so for static methods (i.e. refer to the current class without an instance). this.staticMethod() so I don't have to write the class name 'User'. From MDN documentation Static method calls are made directly on the class and are not callable on instances of the class. Static methods are often used to create utility functions. For more please see=> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/static You can do something like

Can I change the context of javascript “this”?

百般思念 提交于 2019-11-27 15:37:40
问题 var UI$Contract$ddlForm_change = function() { //'this' is currently the drop down that fires the event // My question is can I change the context so "this" represents another object? this = SomeObject; // then call methods on the new "this" this.someMethod(someParam); }; is this possible? 回答1: No, it's not possible. You can call a method with a specified value for this (using method.apply() / method.call() ) but you cannot re-assign the keyword, this . 回答2: You can't change what this refers

Assignment of a struct value to this keyword

China☆狼群 提交于 2019-11-27 15:26:26
问题 I was recently looking into internals of CancellationToken structure and discovered a bit of weird construct (to be more precise, assignment of value to this keyword). Code of one of its constructors is as following: public CancellationToken( bool canceled ) { this = new CancellationToken(); if ( canceled ) { this.m_source = CancellationTokenSource.InternalGetStaticSource( canceled ); } } What is the meaning of line on which the assignment to this keyword occurs? Please note that assignment

How to pass this by ref in C#?

ε祈祈猫儿з 提交于 2019-11-27 15:04:49
In a class (ClassA) of mine I want to create a related instance of another class (ClassB) providing it with a reference to the object who has initiated it's creation. So I've provided ClassB with a construcror taking a (ref ClassB master) argument. But in ClassA I can't just call var slave = new ClassB(ref this). How to implement this? The ref keyword causes Pass by Reference semantics - that is, if the variable is re-assigned in the called function, it will re-assign the variable in the caller as well. Obviously, this only works if a variable 2 (which can be re-assigne to) is directly passed

Should I use “this” keyword when I want to refer to instance variables within a method?

僤鯓⒐⒋嵵緔 提交于 2019-11-27 14:58:08
My teacher says that when I try to access an instance variable within a method I should always use the this keyword, otherwise I would perform a double search. A local scope search and then an instance scope search. Example: public class Test(){ int cont=0; public void Method(){ System.out.println(cont);//Should I use This.cont instead? } } I hope he is wrong, but I can't find any argument. No, only use this when you have a name conflict such as when a method parameter has the same name as an instance field that it is setting. It can be used at other times, but many of us feel that it simply

Using 'this' keyword in Java constructors [duplicate]

纵然是瞬间 提交于 2019-11-27 14:57:02
问题 This question already has an answer here: What is the meaning of “this” in Java? 19 answers I am confused with the this keyword in Java. If a class has two constructors and we use the this keyword in some method, the object represented by this is instantiated using which of the two constructors? 回答1: You have to distinguish between this. and this() , so to speak: Most of the time, you use this as the reference to the current object, i.e. the reference of this object is replaced at runtime for

How to pass context to forEach() anonymous function [duplicate]

丶灬走出姿态 提交于 2019-11-27 14:46:03
问题 This question already has answers here : The invocation context (this) of the forEach function call (5 answers) Closed 2 years ago . What's the modern and correct way to pass the this context to an anonymous forEach function? function Chart() { this.draw = function(data) { data.forEach(function(value) { //do something with values console.log(this); //question: how to get Chart instead of global scope? )}; }); }; 回答1: Store the current this in some other variable in Chart like this function

What does 'return *this' mean in C++?

你。 提交于 2019-11-27 14:16:43
问题 I'm converting a C++ program to C#, but this part has me confused. What does return *this mean? template< EDemoCommands msgType, typename PB_OBJECT_TYPE > class CDemoMessagePB : public IDemoMessage, public PB_OBJECT_TYPE { (...) virtual ::google::protobuf::Message& GetProtoMsg() { return *this; } } How would it translate into C#? 回答1: this means pointer to the object, so *this is an object. So you are returning an object ie, *this returns a reference to the object. 回答2: Watch out that if you

Why can iterators in structs modify this?

时间秒杀一切 提交于 2019-11-27 14:00:04
问题 I discovered that iterator methods in value types are allowed to modify this. However, due to limitations in the CLR, the modifications are not seen by the calling method. ( this is passed by value) Therefore, identical code in an iterator and a non-iterator produce different results: static void Main() { Mutable m1 = new Mutable(); m1.MutateWrong().ToArray(); //Force the iterator to execute Console.WriteLine("After MutateWrong(): " + m1.Value); Console.WriteLine(); Mutable m2 = new Mutable()

What is the reason for var $this = this

人盡茶涼 提交于 2019-11-27 13:46:01
问题 I'm not the best at jquery and I came across a var initialization that I don't know why the person who wrote the code did it this way. In the init for a plugin, we have this.init = function(settings) { var $this = this; this.s = { initialSlide: 0, firstSlide: true, }; ... more code, some uses $this, some uses "this" } So what is the difference here between "$this" and "this" and why not use one or the other all the time? 回答1: Generally, this means a copy of this . The thing about this is that