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34 lines
1.3 KiB
Plaintext
34 lines
1.3 KiB
Plaintext
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created: 20190205023543910
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modified: 20190217012121130
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tags:
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title: Widget attributes tutorial part II
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type: text/vnd.tiddlywiki
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This example will build on the previous one. The only modification will be to add a check to the `refresh` method. The `refreshSelf` will only be called if a change to the attributes is detected.
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The `computeAttributes` method returns a Javascript object containing properties for each attribute which has changed. So a check like `if (changedAttributes.attr1 || changedAttributes.attr2 || changedAttributes.attr3)` etc. can be used to detect the change. See the refresh method in [[$:/core/modules/widgets/view.js]] for an example showing the check for multiple attributes.
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For this example, `message` is the only attribute implemented.
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```javascript
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/*
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Refresh if the attribute value changed since render
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*/
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MyWidget.prototype.refresh = function(changedTiddlers) {
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// Find which attributes have changed
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var changedAttributes = this.computeAttributes();
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if (changedAttributes.message) {
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this.refreshSelf();
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return true;
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} else {
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return false;
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}
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};
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```
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The full code can be seen at [[hello-attribute-optimized.js]] and here is the result ([[Widget attributes demo II]]):
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{{Widget attributes demo II}}
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The visible behavior here should be identical to the unoptimized behavior of the previous tutorial.
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