Install

TODO....

Use

Validate-this leverages the builder pattern to handle validation for both entire objects and single values. At the heart of this project is the rule builder class. To create a new rule use the rule method.

const myRule = rule();

Once you have an instance of a ruleBuilder you will be able to use its builder methods to build out custom validation rules. Such as:

const myRuleWithConstraint = myRule.must(..)
const myRuleWithContext = myRule.withContext(..)
const myRuleWithDisplayName = myRule.withDisplayName(..)
const myRuleWithGetter = myRule.withGetter(..)

Each of these methods will return a new instance of the rule with the requested method applied to only the new instance. This is to make it easier to chain rule together like so:

const ctx = {prop:'I am hungry'}
const myRule = rule()
  .must((value)=> !!value)  //Make sure the value is truthy
  .must((value,ctx)=> value !== ctx.prop) // Make sure the value is not equal prop
  .withContext(ctx,true) // Sets the context and makes sure the reference to the original model is preserved

ctx.prop2 = 'I am Full'

const myRule2 = myRule
  .withContext(ctx) // Sets the context to be cloned each time this will preserve the state of the context when withContext was called
  .must((value, ctx)=> value !=== ctx.prop2 )

Building rules like this can make it easy to share common configuration such as all fields are required.

Now to evaluate a rule you have 3 helper functions

const myRule = rule.must(v=>v)

// To evaluate against a value all you have to do is pass the value,
// unless the rule needs a context to run.
// If a context is required then an error will be returned with
// cannotEvaluate flag set to true.  
const resultOfSimpleValueCheck = myRule.evaluate(1);

//To evaluate against a model you must have a getter set. Otherwise undefined will be returned
const resultOfValidationForAContext = myRule.withGetter('count').evaluateFor({count:2}) 

const func = myRule
  .must((_,ctx) => ctx.prop.innerProp.contains('I eat squid for breakfast'))
  .withGetter(ctx=>prop.innerProp)
  .withContext({prop:{innerProp:'Not today!'}})
  .asFunc();

// returns {name:null, error:'Property is Invalid', isInvalid:true}
const result = func(1)

In addition to the ruleBuilder class