問(wèn)題描述

我正在使用 ionic 2 框架，并嘗試使用本地存儲(chǔ)來(lái)存儲(chǔ)網(wǎng)絡(luò)狀態(tài)

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);

有兩個(gè)值可以動(dòng)態(tài)分配給狀態(tài)，強(qiáng)"和弱".

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

我能夠在每個(gè)頁(yè)面初始化時(shí)獲取我的本地存儲(chǔ)狀態(tài)"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);
    });
}

這將返回一個(gè)強(qiáng)"或弱"，這正是我想要的，但是否有任何方法或事件可以動(dòng)態(tài)(在狀態(tài)"值更改時(shí))調(diào)用toCheckStatus()"函數(shù)?

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?

工作流程示例(偽代碼):

Workflow Example (pseudo-code):

1. 在應(yīng)用程序啟動(dòng)時(shí) -> 檢查互聯(lián)網(wǎng)狀態(tài)(后臺(tái)將不斷檢查并更新本地存儲(chǔ)值)
2. 將狀態(tài)存儲(chǔ)到本地存儲(chǔ)
3. 調(diào)用函數(shù)獲取值(我的值變化時(shí)如何動(dòng)態(tài)調(diào)用這個(gè)函數(shù)，有什么方法嗎?)
4. 如果狀態(tài)為弱 -> 顯示弱圖標(biāo)
5. 如果狀態(tài)為強(qiáng) -> 顯示強(qiáng)圖標(biāo)

推薦答案

我的值變化時(shí)如何動(dòng)態(tài)調(diào)用這個(gè)函數(shù)，有什么方法嗎?

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

更好的解決方案是使用 observables.您可以在方法中使用 observables 在屬性更改時(shí)發(fā)出事件，然后執(zhí)行您需要執(zhí)行的代碼.

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.

這是一個(gè)非常簡(jiǎn)單的使用observables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);
    }

然后在你的頁(yè)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);
        });
    }
}

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如果您需要更新視圖中的某些內(nèi)容，因?yàn)楹笈_(tái)發(fā)生了更改，您必須讓 Angular 知道該更改.一種方法是使用 Zones.您可以查看我的答案這里 知道該怎么做.

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.

這篇關(guān)于當(dāng) Ionic 2 中的值發(fā)生變化時(shí)檢索本地存儲(chǔ)值的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！