Number validations

• required: can't be undefined (default: false)

• equal: * equal to passed value

• integer: must be an integer (default: false)

• precision: maximum number of decimal places

• positive: must be positive (default: false)

• negative: must be negative (default: false)

• multiple: must be a multiple of the passed value

• min: ** minimum valid value (works like the >= operator)

• greater: ** must be greater than passed value (works like the > operator)

• max: ** maximum valid value (works like the <= operator)

• less: ** must be smaller than passed value (works like the < operator)

• nullable: accepts null (default: false)

const Pool = attributes({
  depth: {
    type: Number,
    positive: true
  },
  width: {
    type: Number,
    min: { attr: 'depth' }
  },
  length: {
    type: Number,
    greater: { attr: 'width' }
  },
  capacity: {
    type: Number,
    nullable: true
  }
})(class Pool {
  getVolume() {
    return this.depth * this.width * this.length;
  }
});