浏览器刷新后，Ngrx Store重置.如何使应用程序保留状态? [英] Ngrx Store Resets after browser refresh. How to make the application preserve the state?

问题描述

我从一个组件调度动作

this.store.dispatch({type : STORE_TEAMCREST , payload : team.crestURI});

在其他组件中，我使用

this.store.select(state => state.table.teamCrest).subscribe(data => this.teamCrest = data);

如果我的应用程序顺序向前或向后前进，则此方法很好，但是一旦我执行浏览器刷新，状态就会丢失其值.如何保留它的价值，以便在浏览器刷新时起作用?

This works fine if my app is going sequentially backward or forward, but once i do a browser refresh the state loses it's value. How to preserve it's value so that it works on browser refresh?

推荐答案

您的商店具有subscribe函数，该函数将在调度动作的任何时间被调用，并且状态树的某些部分可能已更改.对于一个简单的解决方案，您可以在此处将状态持久保存到本地存储中:

Your store has a subscribe function which will be called any time an action is dispatched, and some part of the state tree may potentially have changed. For a simple solution, you could persist the state to local storage here:

this.store.subscribe(function() {
    localStorage.setItem('state', JSON.stringify(this.store.getState()));
})

此处的文档

请注意，您需要对状态进行字符串化才能将其存储在本地存储中

Notice that you will need to stringify your state to store it in local storage

要使用此状态，您将需要将本地存储状态localStorage.getItem('state')(如果存在)传递为化简器中的默认状态.为此，我通常有一个辅助函数来检查本地存储中是否存在带有键"state"的项，并在该值存在时调用JSON.parse.

To use this state, you will need to pass the local storage state localStorage.getItem('state') (if it exists) as your default state in your reducer. To achieve this, i normally have a helper function check whether an item with key 'state' exists in local storage and calls JSON.parse on the value if it exists.

默认的减速器情况:

default:
        if (retrieveState()) {
            var newState = JSON.parse(retrieveState())          
            return newState
        }
        else {
            return {...whatever your default state is};
        }

在快速浏览之后，似乎确实存在应该实现您想要的中间件:

Also after a quick look around, there does appear to exist a middleware which should achieve what you are wanting: https://github.com/btroncone/ngrx-store-localstorage

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