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							92 lines
						
					
					
						
							2.7 KiB
						
					
					
				## The AdminJS Data model
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Before you dive into the details of the flat helpers, let me briefly introduce the way how the
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database data is stored in AdminJS.
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### The Simple Case
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On the backend all the information from DataBase tables/collections goes to {@BaseRecord#params}
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object. Usually, it is a `{key: value}` store where `key` is a table name, and value could be
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either a string, a number, or an instance of Date() etc.
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On the Frontend - these values go to the corresponding {@link RecordJSON.params} property.
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This is an example `params` property in the "simple case":
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```javascript
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params: {
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  name: 'John',
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  surname: 'Doe',
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  age: 28,
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}
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```
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### The Real World Case
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In the real world:
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* databases have nested JSONB properties or Mixed Schemas
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* developers would like to send more complicated data from the Fronted to the backend as arrays.
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To achieve that we "flatten" all the data before saving them to `params` property.
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So in the real world params could look like:
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```javascript
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params: {
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  name: 'John',
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  surname: 'Doe',
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  age: 28,
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  // nested objects
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  'auth.facebook': 'some login token',
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  'auth.twitter': 'twitter login token',
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  // arrays
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  'interests.0': 'running',
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  'interests.1': 'jogging',
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}
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```
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and all the data can be even nested on the deeper levels.
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### Why we did that?
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An alternative solution would be to store an entire raw object and don't care. But there are 2
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reasons why we picked this one.
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**1. storing selected data in the database**
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If you send to the ORM unflatten save request like this: 
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```javascript
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Model.save({{ auth: { facebook: 'newFacebookToken' } }})
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```
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it will override an entire `auth` property, so from the example above, we will lose `auth.twitter`.
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In the second (flatten) case:
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```javascript
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Model.save({ `auth.facebook`: 'newFacebookToken' }})
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```
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ORM should keep the value of the `auth.twitter`
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> The above is true for Mongoose adapter which is the most advanced regarding handing mixed values
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**2. Sending data between the Frontend and the Backend in {@link https://developer.mozilla.org/en-US/docs/Web/API/FormData FormData} format**
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AdminJS allows you to upload Files from the Frontend to the Backend. The most optimal way of
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doing that is by using {@link https://developer.mozilla.org/en-US/docs/Web/API/FormData FormData}.
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But, this requires that values for all the fields are send in `[key: string]: string` form.
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And this, as you might guess, fits perfectly to our flatten `params` logic.
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### Consequences
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Flattening in AdminJS has its consequences everywhere where you use
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- {@link BaseRecord} and
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- {@link RecordJSON}, 
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because instead of raw object you have it's flatten version.
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Also, (as mentioned) the `payload` send to the backed is also flattened.
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There you should use helpers gathered in {@link flat} |