69 lines
2.3 KiB
Markdown
69 lines
2.3 KiB
Markdown
---
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tags: [mongo-db, mongoose, node-js]
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---
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# Validating Mongoose schemas
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Let's say we have the following schema:
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```js
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const courseSchema = new mongoose.Schema({
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name: { type: String, required: true, minlength: 5, maxlength: 255 },
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author: String,
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tags: [String],
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data: { type: Date, default: Date.now }, // if unspecified, entry will default to current date
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isPublished: Boolean,
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});
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```
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We set our validation criteria as the second property for each schema value. If
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it does not obtain, an exception will be thrown when we attempt to modify the
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database. This will most likely take the form of a Promise rejection.
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Note that this validation only occurs at the level of Mongoose. There is no
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mechanism for running the validation within the database itself. This is one of
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the ways that Mongo differs from an SQL database where you would be able to set
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the property of `required` for a cell in the table. If we didn't set any
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validation via Mongoose, Mongo would accept whatever we sent to it.
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What is the relationship between this Mongoose validation and the
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[Joi](Validation.md) validation that we
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use when validating API requests in Node/Express? They complement each other. We
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use Joi to validate the client request to the API. If this is valid, the process
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would then move onto the next stage which would be transforming the data from a
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REST request to a database request implemented through Mongoose, where a second
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layer of validation would appy. We would also have validation on the
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client-side.
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## Validator functions
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Instead of simply applying a built-in validator like `required`, we can instead
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pass a function that validates agains the validation status of another property
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in the schema. For instance: make the `price` property required only if the
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entry has `true` for `isPublished`:
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```js
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const courseSchema = new mongoose.Schema({
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...
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isPublished: Boolean,
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price: {
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type: Number,
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required: function() {return this.isPublished}
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}
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});
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```
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## Enum validators
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An enum validator enables us to ensure that whatever value is passed when
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instantiating a document that is of a given schema type, it must be one of a
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finite set of values:
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```js
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const anotherSchema = new mongoose.Schema({
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sex: {
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type: String,
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enum: ["male", "female"],
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},
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});
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```
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