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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
- newValue
{*}:The value set on the property.
- 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
- 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"