Embeer.js ComputedProperty readOnly()用法及代码示例

Ember.js 是一个开源 JavaScript 框架，用于开发基于 Model-View-Controller (MVC) 架构的大型客户端 Web 应用程序。 Ember.js是使用最广泛的前端应用框架之一。它的目的是加速开发并提高生产力。目前，它被大量网站使用，包括 Square、Discourse、Groupon、Linked In、Live Nation、Twitch 和 Chipotle。

ComputedProperty 的 readOnly 方法用于将只读模式设置为计算属性。当它被改变时，它会抛出一个错误。

用法:

computedProperty( // property algo ).readOnly();

Parameters: 它不需要任何参数。

Returns: 它返回对象的ComputedProperty。

安装和运行 Ember.js 的步骤：

步骤 1：要运行以下示例，您需要有一个 ember 项目。要创建一个，您需要先安装ember-cli。在终端中写入以下代码：

npm install ember-cli

第 2 步：现在，您可以通过输入以下代码来创建项目：

ember new <project-name> --lang en

步骤 3：要启动服务器，请键入：

ember serve

示例 1：键入以下代码以生成本示例的路由：

ember generate route temp1

应用程序/路线/temp1.js

Javascript


import Route from '@ember/routing/route'; 
import EmberObject from '@ember/object'; 
import Ember from 'ember'; 
import { computed, set } from '@ember/object'; 
  
  
const Person = EmberObject.extend({ 
    toStringExtension() { 
        return this.get('fullName'); 
    }, 
    fullName: computed('firstName', 'lastName', { 
        get() { 
            return `${this.firstName} ${this.lastName}`; 
        } 
    }).readOnly() 
  
}); 
export default class StudentsRoute extends Route { 
  
    CreateEmployee() { 
        let Employee = Person.create({ 
            firstName: '', 
            lastName: '', 
            gender: '', 
            position: '', 
            Salary: 0, 
            email: '', 
            mobile: '', 
        }); 
        return Employee; 
    } 
    setDetails() { 
        this.employee.setProperties({ 
            'firstName': 'Satyam', 'lastName': 'Sahu', 'gender': 'M', 
            'position': 'Software Engneer', 
            'email': 'yogesh@gmail.com', 'mobile': '9382938239', 
            'Salary': 90000 
        }) 
    } 
    model() { 
        this.employee = this.CreateEmployee(); 
        this.setDetails(); 
        try { 
            this.employee.fullName = 'Sam Snehil'
        } catch (error) { 
            console.log('Cannot Change the fullName of '
                + this.employee.toString()) 
        } 
        return this.employee; 
    } 
    setupController(controller, model) { 
        super.setupController(controller, model); 
        controller.set('employee', this.employee); 
    } 
}

应用程序/模板/temp1.hbs

HTML


{{page-title "ComputedProperty readOnly"}} 
<h1>Employee Details:</h1> 
<div>Name: {{this.employee.fullName}}</div> 
<div>Gender: {{this.employee.gender}}</div> 
<div>Position: {{this.employee.position}}</div> 
<div>Salary: {{this.employee.Salary}}</div> 
<div>Mobile: {{this.employee.mobile}}</div> 
<div>Email: {{this.employee.email}}</div> 
{{outlet}}

输出：

输出1

示例 2：键入以下代码以生成本示例的路由：

ember generate route temp2

应用程序/路线/temp2.js

Javascript


import Route from '@ember/routing/route'; 
import EmberObject from '@ember/object'; 
import Ember from 'ember'; 
import { computed, set } from '@ember/object'; 
  
const Student = EmberObject.extend({ 
    Grade: computed('Grade', { 
        get() { 
  
            let m = this.Marks; 
            return m > 80 ? 'A' : 
                m > 65 ? 'B' : m > 50 ? 'C' : 'D'; 
        } 
    }).readOnly(), 
  
    toStringExtension() { 
        return this.get('fullName'); 
    }, 
}); 
export default class WebsitesRoute extends Route { 
  
    students = [ 
        Student.create({ 
            fullName: 'Sam Snehil', 
            Marks: 72, 
            class: 11, 
        }), 
        Student.create({ 
            fullName: 'Ram Sahu', 
            Marks: 84, 
            class: 10, 
        }), 
        Student.create({ 
            fullName: 'Soham Verma', 
            Marks: 69, 
            class: 12, 
        }), 
        Student.create({ 
            fullName: 'David Tigga', 
            Marks: 53, 
            class: 9, 
        }), 
        Student.create({ 
            fullName: 'Pokhu Verma', 
            Marks: 95, 
            class: 10, 
        }), 
        Student.create({ 
            fullName: 'Satyam Verma', 
            Marks: 75, 
            class: 12, 
        }), 
    ]; 
  
    temp; 
    temp2; 
    model() { 
        return this.students; 
    } 
    setupController(controller, model) { 
        super.setupController(controller, model); 
        controller.set('students', this.students); 
        controller.set('temp', this.temp); 
        controller.set('temp2', this.temp2); 
    } 
}

应用程序/控制器/temp2.js

Javascript


import Ember from 'ember'; 
  
export default Ember.Controller.extend({ 
    actions: { 
  
        ChangeGrade(data, data1) { 
            this.students.forEach(function (item) { 
                if (item.fullName == data) { 
                    try { 
                        item.setProperties({ 'Grade': data1 }); 
  
                    } catch (error) { 
                        console.log('Cannot Change the Grade of : ', 
                            item.toString()); 
                    } 
                } 
            }); 
        }, 
    }, 
});

应用程序/模板/temp2.hbs

HTML


{{page-title "ComputedProperty readOnly"}} 
<h3>List of Item in Buckets</h3> 
<table> 
    <tr> 
        <th> Name </th> 
        <th>Class </th> 
        <th>Marks </th> 
        <th>Grade </th> 
    </tr> 
    {{#each @model as |temp|}} 
    <tr> 
        <td>{{temp.fullName}}</td> 
        <td>{{temp.class}}</td> 
        <td>{{temp.Marks}}</td> 
        <td>{{temp.Grade}}</td> 
    </tr> 
    {{/each}} 
</table> 
<br /> 
<div> 
    <label>Enter Name : </label> 
    {{input value=this.item}} 
</div><br /> 
  
  
<div> 
    <label>Change Grade : </label> 
    {{input value=this.item2}} 
</div><br /> 
  
<input
    type="button"
    id="Change-Property"
    value="Change Grade"
    {{action "ChangeGrade" this.item this.item2}} 
/> 
<br /><br /> 
{{outlet}}

输出：

输出2

参考：https://api.emberjs.com/ember/4.9/classes/ComputedProperty/methods/readOnly?anchor=readOnly

相关用法

注：本文由纯净天空筛选整理自jeemains0neet大神的英文原创作品 Ember.js ComputedProperty readOnly() Method。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。