React-Native + Redux: Random number of form fields - react-native

Question

I am a newbie to react-native, redux and saga and have run into a use case that I have not been able to find a solution for. I understand how to map state to properties and pass around the state between action, reducer and saga. This makes sense to me so far. This is where things seem to get dicey. I have a form that requires a variable number of form fields at any given time depending upon what is returned from the database.
As an example, let's say I have a structure like this:
{
name: ‘’,
vehicleMake: ‘’,
vehicleModel: ‘’,
carLotCity: ‘’,
carLotState: ‘’,
carLotZipCode: ‘’,
localPartsManufacturers: [{name: ‘’, address: ‘’, zipCode}]
}
Everything from name to carLotZipCode would only require one text field, however, the localPartsManufacturers array could represent any number of object that each would need their own set of text fields per each object. How would I account for this with redux as far as mapping the fields to the state and mapping the state to the properties? I am confused about how to begin with this scenario. I understand how to project mapping when the fields are fixed.

Answer 1

I would keep the data as it is coming from the backend. That way you'll avoid normalizing it. I think we just have to be smarter when rendering the fields. Here's what I'm suggesting:
function onTextFieldChange(name, index) {
// either name = `name`, `vehicleMake`, ...
// or
// name = `localPartsManufacturers` and `index` = 0
}
function createTextField(name, index) {
return <input
type='text'
name={ name }
onChange={ () => onTextFieldChange(name, index) } />;
}
function Form({ fields }) {
return (
<div>
{
Object.keys(fields).reduce((allFields, fieldName) => {
const field = fields[fieldName];
if (Array.isArray(field)) {
allFields = allFields.concat(field.map(createTextField));
} else {
allFields.push(createTextField(fieldName));
}
return allFields;
}, [])
}
</div>
);
}
Form receives all the data as you have it in the store. Then we check if the field is an array. If it is an array we loop over the fields inside and generate inputs same as the other properties createTextField. The tricky part here is how to update the data in the store. Notice that we are passing an index when the text field data is changed. In the reducer we have to write something like:
case FIELD_UPDATED:
const { name, index, value } = event.payload;
if (typeof index !== 'undefined') {
state[name][index] = value;
} else {
state[name] = value;
}
return state;

Answer 2

There is nothing preventing you from keeping a list, map, set or any other object in Redux.
The only thing remaining then, is how you map the state to your props, and how you use them. Instead of mapping a single element from the collection to a prop, you map the entire collection to a single prop, and then iterate over the collection in your render method.
In the action you can pass a new collection back, which is comprised of the form fields making up the parts list. Then, your reducer will replace the collection itself.
Or, upon changing an element in the part collection, you can send an action with its id, find it in the collection in the reducer and replace the element that was changed / add the new one / remove the deleted one.