switch transformer

var rule = {
  value: { // following switch is a rule applied to field 'value'
    'switch': 'type',
    'cases': {
      'string': ['mandatory', {validate: 'string', minLength: 4}],
      'number': ['notMandatory', {validate: 'number', min: 10}]
    },
    // default is optional, if no case matches, run default rule
    'default': 'mandatory'
  }
};

validation.validate({value: 'on', type: 'string'}, rule);
// => { value: [ 'must have at least 4 characters' ] }

validation.validate({value: 5, type: 'number'}, rule);
// => { value: [ 'must be at least 10' ] }

switch transformer can also be used in nested context, it’s smart enough to figure out the context. Following rule can produce exact same error.

var rule = { // following switch is a rule in nested context
  'switch': 'type', // type is in nested context now
  'cases': {
    'string': {
      // nested rule
      value: ['mandatory', {validate: 'string', minLength: 4}]
    },
    'number': {
      // nested rule
      value: ['notMandatory', {validate: 'number', min: 10}]
    }
  },
  // default is optional, if no case matches, run default rule
  'default': {
    value: 'mandatory'
  }
};

validation.validate({value: 'on', type: 'string'}, rule);
// => { value: [ 'must have at least 4 characters' ] }

validation.validate({value: 5, type: 'number'}, rule);
// => { value: [ 'must be at least 10' ] }

The “switch” key accepts either expression or function. The result of the expression/function must be a string, which is used for “cases” lookup.

Without switch transformer, you still can use multiple “if” conditional rules to do the same thing.

The only reason for using “readyToUse” mode to implement switch transformer, is to smartly support both normal mode and nested mode. If cut off support of nested mode, switch transformer can be implemented in normal transformer by simply reusing if transformer.

Let’s move on to the foreach transformer.