Override writing behavior
Forest Admin allows replacing the field writing behavior with your own.
This is useful when you want to change how a given field behaves, but also to make computed fields writable.
The
replaceFieldWriting
function allows changing the behavior of any change by creating a new patch that will be applied to the record.You should refrain from using handlers that have side effects (to perform error handling, validation, ...) and use hooks instead.
Making a field read-only can be achieved by passing
null
as an update handler.collection.replaceFieldWriting('fullName', null);
In the following example, editing or creating a
fullName
will update both firstName
and lastName
fields of the record.collection.replaceFieldWriting('fullName', value => {
const [firstName, lastName] = value.split(' ');
return { firstName, lastName };
});
You can have different behavior for
creations
and updates
.In this example, each time the
firstName
field is edited, we also want to update a timestamp field.collection.replaceFieldWriting('firstName', async (value, context) => {
switch (context.action) {
case 'create':
return { firstName, firstNameLastEdited: null };
case 'update':
return { firstName, firstNameLastEdited: new Date().toISOString() };
default:
throw new Error('Unexpected value');
}
});
Handling relationships inside a
replaceFieldWriting
will only work for ManyToOne
and OneToOne
relationships.In this simple example, we have two collections that are linked together:
- The
Users
collection has ajob
and aportfolioId
as foreignKey - The
Portfolios
collection has atitle
When the user updates his
job
field we want also to update the title
of the portfolio by the job
name.collection.replaceFieldWriting('job', (job, { action }) => {
return { job, portfolio: { title: job } };
});
If the relationships do not exist it will create them with the given field values.
You can also provide another
portfolioId
to update the relationships and their fields:collection.replaceFieldWriting('job', (job, { action }) => {
return { job, portfolioId: 8, portfolio: { title: job } };
});
Of course, you can chain the relationships. For example, if a portfolio has a
one-to-one
relationship with the formats
collection, you can update it by writing the right path.collection.replaceFieldWriting('job', (job, { action }) => {
return { job, portfolioId: 8, portfolio: { title: job, format: { name: 'pdf' } } };
});
Last modified 3mo ago