angularjs: trigger form validate programmatically (inside a controller) - forms

Question

I have this situation in which I show 1 form in two steps. So to proceed to the second part of the form you have to click on a button. But before moving on I would like to perform form validation (all required fields need to be filled in). But because this is a normal button, the whole submit magic is not triggered and the validation does not happen. So the question I'm interested in is how can I trigger form validation in my controller ? It would even be better to trigger validation for specific fields. Just to give an idea, the form looks like
<form name="form" submit="save()">
<section id="step1">
<label for="username" required>Username</label>
<input type="text" name="username" ng-model="user.username" required />
.....
<button ng-click="proceed()">Proceed</button>
</section>
<section id="step2">
<label ...></label>
<input...>
....
<button type="submit">Save</button>
</section>
</form>
Also, I don't want to opt for disabling the button until all required fields are valid.

Answer 1

Take a look at the ng-form directive. It allows nesting forms (actually not HTML <form>s, but Angular NgFormControllers). So you can split your one form, used for posting to the server, into two logical forms, used for independent validation:
<form submit="save()">
<div ng-form="form1">
...controls...
<button ng-click="proceed()"
ng-disabled="form1.$invalid">Proceed</button>
</div>
<div ng-form="form2">
...controls...
<button type="submit"
ng-disabled="form2.$invalid || form1.$invalid">Submit</button>
</div>
</form>

Answer 2

You can access the $valid property from your controller. Something like this could work.
$scope.proceed = function(){
if($scope.form.username.$valid){
//username is valid we may proceed to the next step
}
};

Answer 3

<button ng-click="proceed()">Proceed</button>
Replace To :
<button ng-click="proceed()" ng-disabled="form.$invalid">Proceed</button>
Button will not visible button until all required fields are valid.
DEMO