当Ionic 2中的值发生变化时，检索localstorage值 [英] Retrieve localstorage value when value is change in Ionic 2

问题描述

我正在使用离子2框架，我尝试使用本地存储来存储网络状态

I am using ionic 2 framework and I have tried using local storage to store a network status

this.local = new Storage(LocalStorage);
this.local.set("status", this.status);

有两个值，强和弱可以动态分配给状态。

There are 2 values that, "Strong" and "Weak" that can be assigned to status dynamically.

我能够在每个页面的初始化时获得本地存储status值的初始值。

I am able to get my the initial value of my local storage "status" value on initialization of every page.

toCheckStatus();
function toCheckStatus()
{
    self.local = new Storage(LocalStorage);
    self.local.get('status').then((value) => 
    {
        console.log("status", value);
    });
}

这会给我一个强或弱，这是什么我想，但是有没有动态的方法或事件（Onstatus值改变）调用toCheckStatus（）函数？

this will return me a "Strong" or "Weak", which is what I want, but is there any methods or event to dynamically (On "status" value change) call "toCheckStatus()" function?

工作流示例（伪代码） ：

Workflow Example (pseudo-code):

1. 在应用程序启动时 - >检查互联网状态（后台将继续检查并更新本地存储值）


2. 将状态存储到本地存储


3. 调用函数以获取值（如果我的值更改时如何动态调用此函数，是否有任何方法？）


4. 如果状态为弱 - >显示弱图标


5. 如果状态强 - >显示强势图标

1. On application start -> Check internet status (Background will keep checking and update local-storage value)
2. Store status to local-storage
3. Call a function to get the value (How to dynamically call this function when my value change, is there any method?)
4. If Status is Weak -> Show Weak Icon
5. If Status is Strong -> Show Strong icon

推荐答案

如果我的值发生变化，如何动态调用此函数，是否有任何方法？

How to dynamically call this function when my value change, is there any method?

更好的解决方案是使用 observables 。您可以在方法中使用 observables 在更改属性时发出事件，然后执行您需要执行的代码。

A better solution will be using observables. You can use observables in your methods to emit events when a property is changed and then execute the code you need to execute.

这是使用 observables 的一个非常简单的例子：

This is a very simple example of using observables:

import {Injectable} from '@angular/core';
import {Observable} from 'rxjs/Observable';

@Injectable()
export class StorageService {

    private storageObserver: any;
    public storage: any;

    constructor(...) {
        this.storageObserver= null;

        this.storage= Observable.create(observer => {
            this.storageObserver= observer;
        });
    }

    public yourMethod(): void { 

        // This method changes the value of the storage
        // ...

        // Notify to the subscriptor that the value has changed
        this.storageObserver.next(newValue);
    }

然后在你的页面中：

@Component({
  templateUrl: 'build/pages/my-new-page/my-new-page.html',
  providers: [..., StorageService ]
})
export class MyNewPage {

    constructor(..., private storageService : StorageService ) {

        // Initialize all the things you need
        // ... 

        this.storageService.storage.subscribe((newValue) => {
                // This code will execute when the property has changed and also
                // you'll have access to the object with the information that
                // your service sent in the next() call.
                this.doWhatYouWant(newValue);
        });
    }
}

=========== ================================

===========================================

编辑：

如果您需要更新视图中的内容，请注意背景中已更改的内容，您必须让Angular知道更改。一种方法是使用区域。你可以查看我的答案这里知道怎么做。

If you need to update something in the view, beacuse of something that has changed in the background, you will have to let Angular know of that change. One way to do it is by using Zones. You can check my answer here to know how to do it.

这篇关于当Ionic 2中的值发生变化时，检索localstorage值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！