enumeration | 易学教程

What is the difference between for..in and for each..in in javascript?

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问题 What is the difference between for..in and for each..in statements in javascript? Are there subtle difference that I don't know of or is it the same and every browser has a different name for it? 回答1: "for each...in" iterates a specified variable over all values of the specified object's properties. Example: var sum = 0; var obj = {prop1: 5, prop2: 13, prop3: 8}; for each (var item in obj) { sum += item; } print(sum); // prints "26", which is 5+13+8 Source "for...in" iterates a specified

Java getting the Enum name given the Enum Value

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问题 How can I get the name of a Java Enum type given its value? I have the following code which works for a particular Enum type, can I make it more generic ? public enum Category { APPLE("3"), ORANGE("1"), private final String identifier; private Category(String identifier) { this.identifier = identifier; } public String toString() { return identifier; } public static String getEnumNameForValue(Object value){ Category[] values = Category.values(); String enumValue = null; for(Category eachValue

Get to get all child scopes in Angularjs given the parent scope

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问题 I would like to know how to get a list of all child scopes given a parent scope. All I can find from the properties of the scope are $$childHead, $$childTail, $$nextSibling and $$prevSibling. The approach I'm using now is to get the childHead from the parent and then using the nextSibling to get the next child until nextSibling is null. Is there a better approach? Given that I want to call a method [getModel] on all the children, is there again a better way of doing this? 回答1: The child

How to stop enumerateObjectsUsingBlock Swift

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问题 How do I stop a block enumeration? myArray.enumerateObjectsUsingBlock( { object, index, stop in //how do I stop the enumeration in here?? }) I know in obj-c you do this: [myArray enumerateObjectsUsingBlock:^(id *myObject, NSUInteger idx, BOOL *stop) { *stop = YES; }]; 回答1: In Swift 1: stop.withUnsafePointer { p in p.memory = true } In Swift 2: stop.memory = true In Swift 3 - 4: stop.pointee = true 回答2: This has unfortunately changed every major version of Swift. Here's a breakdown: Swift 1

Why aren't Enumerations Iterable?

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问题 In Java 5 and above you have the foreach loop, which works magically on anything that implements Iterable : for (Object o : list) { doStuff(o); } However, Enumerable still does not implement Iterable , meaning that to iterate over an Enumeration you must do the following: for(; e.hasMoreElements() ;) { doStuff(e.nextElement()); } Does anyone know if there is a reason why Enumeration still does not implement Iterable ? Edit: As a clarification, I'm not talking about the language concept of an

case class copy 'method' with superclass

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问题 I want to do something like this: sealed abstract class Base(val myparam:String) case class Foo(override val myparam:String) extends Base(myparam) case class Bar(override val myparam:String) extends Base(myparam) def getIt( a:Base ) = a.copy(myparam="changed") I can't, because in the context of getIt, I haven't told the compiler that every Base has a 'copy' method, but copy isn't really a method either so I don't think there's a trait or abstract method I can put in Base to make this work

Overriding Scala Enumeration Value

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问题 As far as I can tell, Scala has definitions for the Enumeration Value class for Value(Int), Value(String), and Value(Int, String). Does anyone know of an example for creating a new Value subclass to support a different constructor? For example, If I want to create an Enumeration with Value(Int, String, String) objects, how would I do it? I would like all of the other benefits of using the Enumeration class. Thanks. 回答1: The Enumeration values are instance of the Val class. This class can be

scala.Enumeration 枚举示例

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 简介在Scala中并没有枚举类型，但在标准类库中提供了Enumeration类来产出枚举。扩展Enumeration类后，调用Value方法来初始化枚举中的可能值。内部类Value实际上是一个抽象类，真正创建的是Val。因为实际上是Val，所以可以为Value传入id和name 如果不指定，id就是在前一个枚举值id上加一，name则是字段名 scala枚举示例 object TrafficLightColor extends Enumeration { type TrafficLightColor = Value val Red = Value(0, "Stop") val Yellow = Value(10) val Green = Value("Go") } object Margin extends Enumeration { type Margin = Value val TOP, BOTTOM, LEFT, RIGHT = Value } import test.TrafficLightColor._ import test.Margin._ object Driver extends App { println(BOTTOM, BOTTOM.id) def doWhat(color:

BitArray returns bits the wrong way around?

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问题 This code: BitArray bits = new BitArray(new byte[] { 7 }); foreach (bool bit in bits) { Console.WriteLine(bit ? 1 : 0); } Gives me the following output: 11100000 Shouldn't it be the other way around? Like this: 00000111 I am aware that there is little and big endian, although those terms only refer to the position of bytes. As far as I know, they don't affect bits. 回答1: The documentation for BitArray states: The first byte in the array represents bits 0 through 7, the second byte represents

How to add a method to Enumeration in Scala?

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问题 In Java you could: public enum Enum { ONE { public String method() { return "1"; } }, TWO { public String method() { return "2"; } }, THREE { public String method() { return "3"; } }; public abstract String method(); } How do you do this in Scala? EDIT / Useful links: https://github.com/rbricks/itemized http://pedrorijo.com/blog/scala-enums/ 回答1: Here is an example of adding attributes to scala enums by extending the Enumeration.Val class. object Planet extends Enumeration { protected case