computed-properties

问题 How can I use computed property in lists. I am using VueJS v2.0.2. Here's the HTML: <div id="el"> <p v-for="item in items"> <span>{{fullName}}</span> </p> </div> Here's the Vue code: var items = [ { id:1, firstname:'John', lastname: 'Doe' }, { id:2, firstname:'Martin', lastname: 'Bust' } ]; var vm = new Vue({ el: '#el', data: { items: items }, computed: { fullName: function(item) { return item.firstname + ' ' + item.lastname; }, }, }); 回答1: You can't create a computed property for each

问题 I'm new to Swift. What is the difference between a computed property and a property set to a closure? I know a computed property gets recalculated each time. Is it different for the closure? i.e. Closure: var pushBehavior: UIPushBehavior = { let lazilyCreatedPush = UIPushBehavior() lazilyCreatedPush.setAngle(50, magnitude: 50) return lazilyCreatedPush }() Computed: var pushBehavior: UIPushBehavior { get{ let lazilyCreatedPush = UIPushBehavior() lazilyCreatedPush.setAngle(50, magnitude: 50)

问题 I have the following class: class ReportView: NSView { var categoriesPerPage = [[Int]]() var numPages: Int = { return categoriesPerPage.count } } Compilation fails with the message: Instance member \'categoriesPerPage\' cannot be used on type \'ReportView\' What does this mean? 回答1: You just have syntax error when saying = {return self.someValue} . The = isn't needed. Use : var numPages: Int { get{ return categoriesPerPage.count } } if you want get only you can write var numPages: Int {

问题 What is the main difference between a method and a computed value in Vue.js? They look the same and interchangeable. 回答1: Computed values and methods are very different in Vue and are definitely not interchangeable in most cases. Computed Property A more appropriate name for a computed value is a computed property. In fact, when the Vue is instantiated, computed properties are converted into a property of the Vue with a getter and sometimes a setter. Basically you can think of a computed

问题 EDIT: this is a duplicate, see here I can\'t find any examples of using a dynamic key name when setting the state. This is what I want to do: inputChangeHandler : function (event) { this.setState( { event.target.id : event.target.value } ); }, where event.target.id is used as the state key to be updated. Is this not possible in React? 回答1: Thanks to @Cory's hint, i used this: inputChangeHandler : function (event) { var stateObject = function() { returnObj = {}; returnObj[this.target.id] =