CODEWITHSUNDEEP
javascriptreactjsreact-nativejavascript-objects
bozzmob
bozzmob

Reputation: 12574

React Native : Attempted to assign to readonly property

I am trying to check if the entry exists in the AsycStore and if it doesn't exist then, I create an object and set it. And there is a return statement that returns the dataobject.

Here is the pseudocode-

AsyncStorage.getItem("dataobject").then((do) => {
  if(do == undefined)
  {
    console.log("initializing obj + setting data");
    var dobj = "data object";
    dobj.isdirty = true;
    AsyncStorage.setItem("dataobject",dobj);
  }
  return AsyncStorage.getItem("dataobject");
}).done();
},

I am getting an error in console -

W/ReactNativeJS: 'Error: Attempted to assign to readonly property.\n stack: \n  <unknown>

index.android.bun…:53047\n  tryCallOne                           
index.android.bun…:5094\n  <unknown>                            
index.android.bun…:5160\n  <unknown>                            
index.android.bun…:3399\n  callTimer                            
index.android.bun…:2954\n  callImmediates                       
index.android.bun…:3003\n  <unknown>                            
index.android.bun…:2523\n  guard                                
index.android.bun…:2452\n  __callImmediates                     
index.android.bun…:2523\n  <unknown>                            
index.android.bun…:2503\n  guard                                
index.android.bun…:2452\n  invokeCallbackAndReturnFlushedQueue  index.android.bun…:2501\n URL: http://localhost:8081/index.android.bundle?platform=android&dev=true\n line: 53047\n message: Attempted to assign to readonly property.'

I am not really sure what is the readonly property I am trying to assign. The line number that is being warned is this line - "dobj.isdirty = true";

Should I not add a property to an object? How do I solve this problem? What's the right way of doing it?

Screenshot-

Attempted to assign to readonly property width=100

Upvotes: 5

Views: 31347

Answers (2)

oliversisson
oliversisson

Reputation: 2309

Is dobj a string or an object?

var dobj = "data object"; dobj.isdirty = true;

In the second line, dobj.isdirty is undefined and you're trying to set that ("undefined" is a readonly property of JS).

Now if you're trying to do

var dobj = {}; dobj.isdirty = true;

Then instead you should do

var dobj = {}; dobj['isdirty'] = true;

OR

var dobj = {isdirty: true};

Upvotes: -3

Nader Dabit
Nader Dabit

Reputation: 53691

You can probably accomplish this by using the .catch, which should throw if there is not a value there. Something like:

AsyncStorage.getItem("dataobject")
.then((do) => {
  this.setState({
    myData: do.toJSON();
  })
})
.catch(() => {
   console.log("initializing obj + setting data");
   var dobj = {};
   dobj.isdirty = true;
   AsyncStorage.setItem("dataobject",JSON.stringify(dobj));
});

Upvotes: 5

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