AsyncStorage.getItem 返回 undefined :React Native [英] AsyncStorage.getItem returns undefined : React Native

问题描述

代码流是-

我正在检查 AsyncStorage 中是否存在名为 listobject 的条目.

1. 如果它不存在，那么我创建一个对象，添加一些属性并设置存储.我将商店送到 obj，因为我必须在下一个 if 条件下进行比较.

2. 如果listobject条目已经存在(第二次)，那么，它直接来到第二块，并进行比较.(我在第一步中为 obj 获取值的原因是因为我可以有一个常见的 obj.data.isdirty 条件.

这是我的代码-

AsyncStorage.getItem('listobject').then((obj) => {如果(对象 == 未定义){var obj1 ={};obj1.data ={};obj1.data.isdirty = true;console.log("obj1 = "+ JSON.stringify(obj1));AsyncStorage.setItem('listobject',obj1);obj = AsyncStorage.getItem('listobject');console.log("obj = "+ JSON.stringify(obj));}如果(obj.data.isdirty){obj.data.isdirty = false;AsyncStorage.setItem('listobject',JSON.stringify(obj));return AsyncStorage.getItem('listobject');}}).完毕();

我有 2 个问题是同一问题的结果-

1. 日志.我正在设置 obj1 并为 obj 获取相同的值(以便我可以比较下一个 if 条件).为什么我无法获得与设置相同的值?

<块引用>

12-03 00:27:56.281 32598-487/com.abc D/ReactNativeJS:'obj1 = {data":{isdirty":true}}'

12-03 00:27:56.286 32598-487/com.abc D/ReactNativeJS:'obj = {_37":0，_12":null，_59":[]}'

2. 这是上述日志的最终结果.我得到 list.data.isdirty 未定义.我想这是因为 obj 中不存在我正在访问的 JSON 格式，即 obj.data.isdirty 不存在.那么，我该如何克服这个问题?

<块引用>

undefined 不是一个对象(评估 'list.data.isdirty')；

请告诉我我做错了什么?

解决方案

我实际上是将对象从一个复制到另一个.成功了.

AsyncStorage.getItem('listobject').then((obj) => {如果(对象 == 未定义){var obj1 ={};obj1.data ={};obj1.data.isdirty = true;console.log("obj1 = "+ JSON.stringify(obj1));AsyncStorage.setItem('listobject',obj1);obj = obj1;//这就是我所做的！console.log("obj = "+ JSON.stringify(obj));}如果(obj.data.isdirty){obj.data.isdirty = false;AsyncStorage.setItem('listobject',JSON.stringify(obj));return AsyncStorage.getItem('listobject');}}).完毕();

Codeflow is-

I am checking if an entry called listobject exists in the AsyncStorage.

1. If it doesn't exist, then, I create an object, add few attributes and set the store. I get the store to obj as I have to compare in the next if condition.

2. If the listobject entry already exists(2nd time), then, it directly comes to the 2nd block, and compares. (The reason I get values to obj in 1st step is because I can have a common obj.data.isdirty condition.

Here is my code-

AsyncStorage.getItem('listobject').then((obj) => {
    if(obj == undefined)
    {
        var obj1 ={};
        obj1.data ={};
        obj1.data.isdirty = true;
        console.log("obj1 = "+ JSON.stringify(obj1));
        AsyncStorage.setItem('listobject',obj1);
        obj = AsyncStorage.getItem('listobject');
        console.log("obj = "+ JSON.stringify(obj));
    }
    if(obj.data.isdirty)
    {
        obj.data.isdirty = false;
        AsyncStorage.setItem('listobject',JSON.stringify(obj));
        return AsyncStorage.getItem('listobject');
    }
}).done();

I have 2 questions which are the outcome of the same issue-

1. Logs. I am setting obj1 and getting the same value for obj (so that I can compare the next if condition). Why am I not able to get the same value that I have set?

12-03 00:27:56.281 32598-487/com.abc D/ReactNativeJS: 'obj1 = {"data":{"isdirty":true}}'

12-03 00:27:56.286 32598-487/com.abc D/ReactNativeJS: 'obj = {"_37":0,"_12":null,"_59":[]}'

2. This is the end result of the above logs. I am getting that list.data.isdirty is undefined. I guess that because the JSON format I am accessing does not exist in obj i.e., obj.data.isdirty doesn't exist. So, how do I overcome this?

undefined is not an object (evaluating 'list.data.isdirty');

Please tell me what am I doing wrong?

解决方案

I actually copied the object from one to another. It worked.

AsyncStorage.getItem('listobject').then((obj) => {
    if(obj == undefined)
    {
        var obj1 ={};
        obj1.data ={};
        obj1.data.isdirty = true;
        console.log("obj1 = "+ JSON.stringify(obj1));
        AsyncStorage.setItem('listobject',obj1);
        obj = obj1; //THIS IS WHAT I DID!
        console.log("obj = "+ JSON.stringify(obj));
    }
    if(obj.data.isdirty)
    {
        obj.data.isdirty = false;
        AsyncStorage.setItem('listobject',JSON.stringify(obj));
        return AsyncStorage.getItem('listobject');
    }
}).done();

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