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The type can be specified as either a type function that returns the type coerced value or one of the following strings:</p> <ul> <li><code>"string"</code> - Converts the value to a string except <code>null</code> or <code>undefined</code>.</li> <li><code>"date"</code> - Converts the value to a date or <code>null</code> if the date can not be converted.</li> <li><code>"number"</code> - Passes the value through <code>parseFloat</code> except for <code>null</code> or <code>undefined</code>.</li> <li><code>"boolean"</code> - Converts falsey, <code>"false"</code> or <code>"0"</code> to <code>false</code> and everything else to true.</li> <li><code>"htmlbool"</code> - Like <code>boolean</code>, but also converts empty strings to <code>true</code>. Used, for example, when input is from component attributes like <code><can-tabs reverse/></code></li> <li><code>"compute"</code> - If the value set is a compute, will allow the returning of the computed value.</li> <li><code>"*"</code> - Prevents the default type coersion of converting Objects to <a href="can-map.html" title="Create observable objects.">Map</a>s and Arrays to <a href="can-list.html" title="">List</a>s.</li> </ul> <h3>Basic Example</h3> <p>The following example converts the <code>count</code> property to a number and the <code>items</code> property to an array:</p> <pre><code> define: { count: {type: "number"}, items: { type: function(newValue){ if(typeof newValue === "string") { return newValue.split(",") } else if( can.isArray(newValue) ) { return newValue; } } } } </code></pre> <p>When a user tries to set those properties like:</p> <pre><code>map.attr({count: "4", items: "1,2,3"}); </code></pre> <p>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].</p> <h3>Preventing Arrays and Objects from Automatic Conversion</h3> <p>When an array is passed into a Map setter, it is automatically converted into a List. Likewise, objects are converted into Map instances. This behavior can be prevented like the following:</p> <pre><code> define: { locations: {type: "*"} } </code></pre> <p>When a user tries to set this property, the resulting value will remain an array.</p> <pre><code>map.attr('locations', [1, 2, 3]); // locations is an array, not a List </code></pre> <h3>Working with the 'compute' type</h3> <p>Setting type as <a href="can-compute.html" title="Create an observable value."><code>compute</code></a> allows for resolving a computed property with the .attr() method.</p> <pre><code class="language-js">MyMap = Map.extend({ define: { value: { type: "compute" } } }); var myMap = new MyMap(); var c = compute(5); myMap.attr("value",c); myMap.attr("value"); //-> 5 c(6); myMap.attr("value"); //-> 6 //Be sure if setting to pass the new compute var c2 = compute("a"); myMap.attr("value",c2); myMap.attr("value"); //-> "a" </code></pre> </section> <script type="text/javascript"> var docObject = {"src":{"path":"node_modules/can-map-define/docs/type.md"},"description":"\nConverts a value passed to [can-map.prototype.attr attr] into an appropriate value.\n","title":"type","name":"can-map-define._type","type":"function","parent":"can-map-define","params":[{"types":[{"type":"*"}],"name":"newValue","description":"The value passed to `attr`."},{"types":[{"type":"String"}],"name":"attrName","description":"The attribute name being set."}],"_curParam":{"types":[{"type":"String"}],"name":"attrName","description":"The attribute name being set."},"context":{"types":[{"type":"Map"}],"description":"the instance of the [can-map Map]."},"returns":{"types":[{"type":"*"}],"description":"The value that should be passed to `set` or (if there is no `set` property) the value to set on the map instance.\n"},"_curReturn":{"types":[{"type":"*"}],"description":"The value that should be passed to `set` or (if there is no `set` property) the value to set on the map instance.\n"},"comment":" ","pathToRoot":".."}; </script> </article> <footer><p>CanJS is part of <a href="http://donejs.com" target="_blank">DoneJS</a>. 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