type

  • function
can.Map.prototype.define.type  

Converts a value passed to attr into an appropriate value.

define.type(newValue, attrName)

Converts a value passed to attr into an appropriate value.

Parameters

  1. newValue {*}

    The value passed to attr.

  2. attrName {String}

    The attribute 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.

This

{can.Map}

the instance of the can.Map.

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 or one of the following strings:

  • "string" - Converts the value to a string except null or undefined.
  • "date" - Converts the value to a date or null if the date can not be converted.
  • "number" - Passes the value through parseFloat except for null or undefined.
  • "boolean" - Converts falsey, "false" or "0" to false and everything else to true.
  • "htmlbool" - Like boolean, but also converts empty strings to true. Used, for example, when input is from component attributes like <can-tabs reverse/>
  • "*" - Prevents the default type coersion of converting Objects to can.Maps and Arrays to can.Lists.

Basic Example

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

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

When a user tries to set those properties like:

map.attr({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 is passed into a can.Map setter, it is automatically converted into a can.List. Likewise, objects are converted into can.Map instances. This behavior can be prevented like the following:

 define: {
   locations: {type: "*"}
 }

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

map.attr('locations', [1, 2, 3]); // locations is an array, not a can.List