angularjs: trigger form validate programmatically (inside a controller)

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>