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type

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Converts a value set on an instance into an appropriate value.

type(newValue, propertyName)

Given the set value, transform it into a value appropriate to be set. type is called before set.

age: {
    type: function(newValue, propertyName){
        return +newValue;
    }
}

Parameters

  1. newValue {*}:

    The value set on the property.

  2. propertyName {String}:

    The property name being set.

Returns

{*}:

The value that should be passed to set or (if there is no set property) the value to set on the map instance.

"typeName"

Sets the type to a named type in types. The default typeName is "observable".

age: {
    type: "number"
}

Parameters

  1. typeName {String}:

    A named type in types.

{propDefinition}

A PropDefinition that defines an inline can-define/map/map type. For example:

address: {
    type: {
        street: "string",
        city: "string"
    }
}

[Type|propDefinition]

Defines an inline can-define/list/list type that's an array of Type or inline propDefinition can-define/map/map instances. For example:

people: {
    type: [Person]
},
addresses: {
    type: [{
        street: "string",
        city: "string"
    }]
}

Use

The type property specifies the type of the attribute. The type can be specified as either:

  • A type function that returns the type coerced value.
  • A named type in types.
  • An object that gets converted into an inline DefineMap.
  • An array that gets converted to an inline DefineList.

Basic Example

The following example converts the count property to a number and the items property to an array:

DefineMap.extend({
    count: {type: "number"},
    items: {
        type: function(newValue){
            if(typeof newValue === "string") {
                return newValue.split(",")
            } else if( Array.isArray(newValue) ) {
                return newValue;
            }
        }
    }
});

When a user tries to set those properties like:

map.set({count: "4", items: "1,2,3"});

The number converter will be used to turn count into 4, and the items type converter function will be used to turn items into [1,2,3].

Preventing Arrays and Objects from Automatic Conversion

When an array value is set, it is automatically converted into a DefineList. Likewise, objects are converted into DefineMap instances. This behavior can be prevented like the following:

 locations: {type: "any"}

When a user tries to set this property, the resulting value will remain an array.

map.locations = [1, 2, 3]; // locations is an array, not a DefineList

Working with the 'compute' type

Setting type as compute allows for resolving a computed property with the .attr() method.

MyMap = DefineMap.extend({
    value: {
        type: "compute"
    }
});

var myMap = new MyMap();
var c = compute(5);

myMap.value = c;
myMap.value //-> 5

c(6);
myMap.value //-> 6

//Be sure if setting to pass the new compute
var c2 = compute("a");
myMap.value = c2;
myMap.value //-> "a"

CanJS is part of DoneJS. Created and maintained by the core DoneJS team and Bitovi. Currently 3.14.1.

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