Trying to change my immutable array in React Native - react-native

Question

I have a function that runs every time your location changes and I'm trying to set a value in my array when a certain if statement is found true. All I seem to be doing is removing everything from my variable except the value that I am changing. Bad explanation so here is some code...
The data starts like this:
this.state = { selectedItem: [] }
And will change to something like this during normal app use:
selectedItem: [{address: 'Somewhere', latitude: -37.826835, longitude: 144.992030, found: false }]
Here is where I am trying to change the data (This will always run after some data is added):
const newSelectedItem = () => {
let copyB = {...this.state.selectedItem};
copyB.found = true;
return copyB;
};
this.setState({selectedItem: newSelectedItem});
When I try to run:
{this.state.selectedItem.address}
I see the initial value which would be the address "Somewhere" but when my function runs based on location change it disappears. What have I actually done to my data in my above function?
Have I just made it selectedItem: [{found:true}] or something dumb like that?

Answer 1

You were doing fine except for one single thing , in this function :
const newSelectedItem = () => {
let copyB = {...this.state.selectedItem};
copyB.found = true;
return copyB;
};
this.setState({selectedItem: newSelectedItem});
here copyB is now an object , but yours selected Item was an array. So the problem is now selectedItem is now an object when you do setState with newSelctedItem.
SO copyB.found = true; wouldnt evaluate anything rather, try copyB[0].found = true; so there the value will be accessed and return true accordingly.
And when you try to access the state , replace {this.state.selectedItem.address}
with {this.state.selectedItem[0].address} ,
Hope i helps. feel free to ask any doubts.
You can play around with this pen codepen

Answer 2

Well, this is pretty weird since you still get the initial value. There are some problems in your code:
You want to store your variables in a array: It's fine, but the problem comes from the way you retrieve and set your value. Since selectedItem, your {this.state.selectedItem.address} because this is an object destructuring. To do that, you have to destruct your array first, e.g: item = selectedItem[0] or using map, etc... After that, you can try: item.address.
Another problem is from your newSelectedItem. Since let copyB = {...this.state.selectedItem}; will destruct your selectedItem, take all its properties and set to newSelectedItem, it will make your selectedItem become an object, not an array anymore.
If your selectedItem stores only 1 object, so don't use array. This selectedItem will become:
selectedItem: {
address: 'Somewhere',
latitude: -37.826835,
longitude: 144.992030,
found: false
}
It looks like a JSON object, hence you can do: selectedItem.address
In case you still don't get it, place a little debug or a console.log("selectedItem", this.state.selectedItem) to see what happend, and you will find out.

Answer 3

I think in the end I was mapping a function to the data and not the data itself. This was my eventual solution...
const newMyWaypoinys = this.state.myWaypoints.map(a => {
let copyA = {...a};
if (copyA.address === wp.address) {
if (copyA.address === this.state.selectedItem.address) {
this.setState(prevState => ({
selectedItem: {
...prevState.selectedItem,
found: true
}
}))
}
copyA.found = true;
}
return copyA;
});
this.setState({
myWaypoints: newMyWaypoinys,
});