Constraints

A Constraint is a simple record used to validate values. Various types of Constraints have already been implemented in API-Flow

Import

/* if in src/ */
import Constraint from './models/Constraint'

Exposed Constraint Records and Usage

• Constraint.Minimum

  const cond = new Constraint.Minimum(4)
  cond.evaluate(3.5) // false
  cond.evaluate(4) // true
  cond.evaluate(4.5) // true
  cond.toJSONSchema() // { minimum: 4 }

• Constraint.ExclusiveMinimum

  const cond = new Constraint.ExclusiveMinimum(4)
  cond.evaluate(3.5) // false
  cond.evaluate(4) // false
  cond.evaluate(4.5) // true
  cond.toJSONSchema() // { minimum: 4, exclusiveMinimum: true }

• Constraint.Maximum

  const cond = new Constraint.Maximum(4)
  cond.evaluate(3.5) // true
  cond.evaluate(4) // true
  cond.evaluate(4.5) // false
  cond.toJSONSchema() // { maximum: 4 }

• Constraint.ExclusiveMaximum

  const cond = new Constraint.ExclusiveMaximum(4)
  cond.evaluate(3.5) // true
  cond.evaluate(4) // false
  cond.evaluate(4.5) // false
  cond.toJSONSchema() // { maximum: 4, exclusiveMaximum }

• Constraint.MultipleOf

  const cond = new Constraint.MultipleOf(0.12)
  cond.evaluate(0.24) // true
  cond.evaluate(0.13) // false
  cond.toJSONSchema() // { multipleOf: 0.12 }

• Constraint.MinimumLength

  const cond = new Constraint.MinimumLength(5)
  cond.evaluate('hey') // false
  cond.evaluate('valid') // true
  cond.evaluate('long enough') // true
  cond.toJSONSchema() // { minLength: 5 }

• Constraint.MaximumLength

  const cond = new Constraint.MaximumLength(5)
  cond.evaluate('hey') // true
  cond.evaluate('valid') // true
  cond.evaluate('too long') // false
  cond.toJSONSchema() // { maxLength: 5 }

• Constraint.Pattern

  const cond = new Constraint.Pattern('^[a-f0-9]*$')
  cond.evaluate('deadbeef') // true
  cond.evaluate('not an hexadecimal string') // false
  cond.toJSONSchema() // { pattern: '^[a-f0-9]*$' }

• Constraint.MinimumItems

  const cond = new Constraint.MinimumItems(4)
  cond.evaluate([ 1, 2, 3 ]) // false
  cond.evaluate([ 1, 2, 3, 4 ]) // true
  cond.evaluate([ 1, 2, 3, 4, 5]) // true
  cond.toJSONSchema() // { minItems: 4 }

• Constraint.MaximumItems

  const cond = new Constraint.MaximumItems(4)
  cond.evaluate([ 1, 2, 3 ]) // true
  cond.evaluate([ 1, 2, 3, 4 ]) // true
  cond.evaluate([ 1, 2, 3, 4, 5 ]) // false
  cond.toJSONSchema() // { maxItems: 4 }

• Constraint.UniqueItems

  const cond = new Constraint.UniqueItems(true)
  cond.evaluate([ 1, 2, 3, 2 ]) // false
  cond.evaluate([ 1, 2, 3, 4, 5 ]) // true
  cond.toJSONSchema() // { uniqueItems: true }

• Constraint.MinimumProperties

  const cond = new Constraint.MinimumProperties(4)
  cond.evaluate({ a: 123, b: 321, c: 234 }) // false
  cond.evaluate({ a: 123, b: 321, c: 234, d: 432 }) // true
  cond.evaluate({ a: 123, b: 321, c: 234, d: 432, e: 345 }) // true
  cond.toJSONSchema() // { minProperties: 4 }

• Constraint.MaximumProperties

  const cond = new Constraint.MaximumProperties(4)
  cond.evaluate({ a: 123, b: 321, c: 234 }) // true
  cond.evaluate({ a: 123, b: 321, c: 234, d: 432 }) // true
  cond.evaluate({ a: 123, b: 321, c: 234, d: 432, e: 345 }) // false
  cond.toJSONSchema() // { maxProperties: 4 }

• Constraint.Enum

  const cond = new Constraint.Enum([ 'abc', 23, 'something' ])
  cond.evaluate('abc') // true
  cond.evaluate(23) // true
  cond.evaluate('not in the list') // false
  cond.toJSONSchema() // { enum: [ 'abc', 23, 'something' ] }

• Constraint.JSONSchema

  const cond = new Constraint.JSONSchema({ type: 'string', enum: [ 'abc', 'def' ] })
  cond.evaluate('abc') // true
  cond.evaluate('def') // true
  cond.evaluate('fgh') // **true**
  cond.toJSONSchema() // { type: 'string', enum: [ 'abc', 'def' ] }

  Note: JSON Schema validation is not yet implemented in API-Flow, and therefore the evaluate method will return true regardless of what is passed to it.

• Constraint.XMLSchema

  const cond = new Constraint.XMLSchema("...")
  cond.evaluate('abc') // true
  cond.evaluate('def') // true
  cond.evaluate('fgh') // **true**
  cond.toJSONSchema() // { x-xml: "..." }

  Note: XML Schema validation is not yet implemented in API-Flow, and therefore the evaluate method will return true regardless of what is passed to it.

Creating a new Constraint

It is possible to create custom constraints to extend the current model.

Example

import Constraint from './models/Constraint'

class CubeIsSmallerThanConstraint extends Constraint.Constraint {
  constructor(value) {
    const instance = {
      _model: new Model({
        name: 'cube-smaller.constraint.models',
        version: '0.1.0'
      }),
      name: 'x-cube-smaller',
      value: value,
      expression: d => {
        if (typeof value !== 'number') {
          return false
        }
        return d*d*d <= value
      }
    }
  }
}

const cond = new CubeIsSmallerThanConstraint(1000)
cond.evaluate(5) // true
cond.evaluate(10) // true
cond.evaluate(15) // false
cond.toJSONSchema() // { 'x-cube-smaller': 1000 }