Ext.data.Field

Fields are used to define what a Model is. They aren't instantiated directly - instead, when we create a class that extends Ext.data.Model, it will automatically create a Field instance for each field configured in a Model. For example, we might set up a model like this:

Ext.define('User', {
    extend: 'Ext.data.Model',
    fields: [
        'name', 'email',
        {name: 'age', type: 'int'},
        {name: 'gender', type: 'string', defaultValue: 'Unknown'}
    ]
});

Four fields will have been created for the User Model - name, email, age and gender. Note that we specified a couple of different formats here; if we only pass in the string name of the field (as with name and email), the field is set up with the 'auto' type. It's as if we'd done this instead:

Ext.define('User', {
    extend: 'Ext.data.Model',
    fields: [
        {name: 'name', type: 'auto'},
        {name: 'email', type: 'auto'},
        {name: 'age', type: 'int'},
        {name: 'gender', type: 'string', defaultValue: 'Unknown'}
    ]
});

Types and conversion

The type is important - it's used to automatically convert data passed to the field into the correct format. In our example above, the name and email fields used the 'auto' type and will just accept anything that is passed into them. The 'age' field had an 'int' type however, so if we passed 25.4 this would be rounded to 25.

Sometimes a simple type isn't enough, or we want to perform some processing when we load a Field's data. We can do this using a convert function. Here, we're going to create a new field based on another:

Ext.define('User', {
    extend: 'Ext.data.Model',
    fields: [
        'name', 'email',
        {name: 'age', type: 'int'},
        {name: 'gender', type: 'string', defaultValue: 'Unknown'},

        {
            name: 'firstName',
            convert: function(value, record) {
                var fullName  = record.get('name'),
                    splits    = fullName.split(" "),
                    firstName = splits[0];

                return firstName;
            }
        }
    ]
});

Now when we create a new User, the firstName is populated automatically based on the name:

var ed = Ext.ModelManager.create({name: 'Ed Spencer'}, 'User');

console.log(ed.get('firstName')); //logs 'Ed', based on our convert function

In fact, if we log out all of the data inside ed, we'll see this:

console.log(ed.data);

//outputs this:
{
    age: 0,
    email: "",
    firstName: "Ed",
    gender: "Unknown",
    name: "Ed Spencer"
}

The age field has been given a default of zero because we made it an int type. As an auto field, email has defaulted to an empty string. When we registered the User model we set gender's defaultValue to 'Unknown' so we see that now. Let's correct that and satisfy ourselves that the types work as we expect:

ed.set('gender', 'Male');
ed.get('gender'); //returns 'Male'

ed.set('age', 25.4);
ed.get('age'); //returns 25 - we wanted an int, not a float, so no decimal places allowed

// example of convert function
function fullName(v, record){
    return record.name.last + ', ' + record.name.first;
}

function location(v, record){
    return !record.city ? '' : (record.city + ', ' + record.state);
}

Ext.define('Dude', {
    extend: 'Ext.data.Model',
    fields: [
        {name: 'fullname',  convert: fullName},
        {name: 'firstname', mapping: 'name.first'},
        {name: 'lastname',  mapping: 'name.last'},
        {name: 'city', defaultValue: 'homeless'},
        'state',
        {name: 'location',  convert: location}
    ]
});

// create the data store
var store = new Ext.data.Store({
    reader: {
        type: 'json',
        model: 'Dude',
        idProperty: 'key',
        root: 'daRoot',
        totalProperty: 'total'
    }
});

var myData = [
    { key: 1,
      name: { first: 'Fat',    last:  'Albert' }
      // notice no city, state provided in data object
    },
    { key: 2,
      name: { first: 'Barney', last:  'Rubble' },
      city: 'Bedrock', state: 'Stoneridge'
    },
    { key: 3,
      name: { first: 'Cliff',  last:  'Claven' },
      city: 'Boston',  state: 'MA'
    }
];

// current sort     after sort we want
// +-+------+          +-+------+
// |1|First |          |1|First |
// |2|Last  |          |3|Second|
// |3|Second|          |2|Last  |
// +-+------+          +-+------+

sortType: function(value) {
   switch (value.toLowerCase()) // native toLowerCase():
   {
      case 'first': return 1;
      case 'second': return 2;
      default: return 3;
   }
}