scope

问题 Working with Futures in Dart, I've come across an interesting issue. import 'dart:async'; class Egg { String style; Egg(this.style); } Future cookEggs(List<Egg> list) => new Future(() => ['omelette','over easy'].forEach((_) => list.add(new Egg(_))) ); Future cookOne(Egg egg) => new Future(() => egg = new Egg('scrambled')); void main() { List<Egg> eggList = new List(); Egg single; cookEggs(eggList).whenComplete(() => eggList.forEach((_) => print(_.style)); cookOne(single).whenComplete(() =>

问题 I have a class that takes some coordinate and duration data. I want to use it to animate an svg . In more explicit terms, I want to use that data to change svg attributes over a time frame. I'm using a step function and requestAnimationFrame outside the class: function step(timestamp) { if (!start) start = timestamp var progress = timestamp - start; var currentX = parseInt(document.querySelector('#start').getAttribute('cx')); var moveX = distancePerFrame(circleMove.totalFrames(), circleMove

问题 I have a class that takes some coordinate and duration data. I want to use it to animate an svg . In more explicit terms, I want to use that data to change svg attributes over a time frame. I'm using a step function and requestAnimationFrame outside the class: function step(timestamp) { if (!start) start = timestamp var progress = timestamp - start; var currentX = parseInt(document.querySelector('#start').getAttribute('cx')); var moveX = distancePerFrame(circleMove.totalFrames(), circleMove

问题 console.log(a) //output:ƒ a(){} var a = 1; function a(){}; var a = 10; console.log(a) //output:10 ==================== var a = 1; if(true){ function a(){}; var a = 10; } console.log(a) // this code throws Uncaught SyntaxError: Identifier 'a' has already been declared both above code snippets are same except the if block.why does the latter throws error when its permissible in javascript to delcare same variable twice in the same scope with var as below function a(){}; var a = 10; //no error

问题 I have a field and a local variable with same name. How to access the field? Code: String s = "Global"; private void mx() { String s = "Local"; lblB.setText(s); // i want global } In c++ use :: operator like following: ::s Is were :: operator in Java? 回答1: That's not a global variable - it's an instance variable. Just use this : String s = "Local"; lblB.setText(this.s); (See JLS section 15.8.3 for the meaning of this .) For static variables (which are what people normally mean when they talk

问题 I have a field and a local variable with same name. How to access the field? Code: String s = "Global"; private void mx() { String s = "Local"; lblB.setText(s); // i want global } In c++ use :: operator like following: ::s Is were :: operator in Java? 回答1: That's not a global variable - it's an instance variable. Just use this : String s = "Local"; lblB.setText(this.s); (See JLS section 15.8.3 for the meaning of this .) For static variables (which are what people normally mean when they talk

问题 What I have known so far is, multiple declarations inside a block produce an error message and also uninitialized local variable gives garbage value on printing. But coming across an example of for loop in C has shaken my concept on the scope of variables. Below is the code for the same: #include<stdio.h> int main() { int i; for(int i = 5; i > 0 ; i--){ int i; printf("%d ", i); } } The above code produces the output 0 0 0 0 0 I have two questions A for loop is considered as one block then how

问题 What I am showing below, is rather a theoretical question. But I am interested in how the new C#7 compiler works and resolves local functions. In C#7 I can use local functions. For example (you can try these examples in LinqPad beta): Example 1: Nested Main() void Main() { void Main() { Console.WriteLine("Hello!"); } Main(); } DotNetFiddle for Example 1 Rather than calling Main() in a recursive way, the local function Main() is being called once, so the output of this is: Hello! The compiler

问题 What I am showing below, is rather a theoretical question. But I am interested in how the new C#7 compiler works and resolves local functions. In C#7 I can use local functions. For example (you can try these examples in LinqPad beta): Example 1: Nested Main() void Main() { void Main() { Console.WriteLine("Hello!"); } Main(); } DotNetFiddle for Example 1 Rather than calling Main() in a recursive way, the local function Main() is being called once, so the output of this is: Hello! The compiler

问题 What I am showing below, is rather a theoretical question. But I am interested in how the new C#7 compiler works and resolves local functions. In C#7 I can use local functions. For example (you can try these examples in LinqPad beta): Example 1: Nested Main() void Main() { void Main() { Console.WriteLine("Hello!"); } Main(); } DotNetFiddle for Example 1 Rather than calling Main() in a recursive way, the local function Main() is being called once, so the output of this is: Hello! The compiler