A DataView offers a filtered and/or formatted view on a DataSet. One can subscribe on changes in a DataView, and easily get filtered or formatted data without having to specify filters and field types all the time.
The following example shows how to use a DataView.
// create a DataSet
var data = new vis.DataSet();
data.add([
{id: 1, text: 'item 1', date: new Date(2013, 6, 20), group: 1, first: true},
{id: 2, text: 'item 2', date: '2013-06-23', group: 2},
{id: 3, text: 'item 3', date: '2013-06-25', group: 2},
{id: 4, text: 'item 4'}
]);
// create a DataView
// the view will only contain items having a property group with value 1,
// and will only output fields id, text, and date.
var view = new vis.DataView(data, {
filter: function (item) {
return (item.group == 1);
},
fields: ['id', 'text', 'date']
});
// subscribe to any change in the DataView
view.subscribe('*', function (event, params, senderId) {
console.log('event', event, params);
});
// update an item in the data set
data.update({id: 2, group: 1});
// get all ids in the view
var ids = view.getIds();
console.log('ids', ids); // will output [1, 2]
// get all items in the view
var items = view.get();
A DataView can be constructed as:
var data = new vis.DataView(dataset, options)
where:
dataset is a DataSet or DataView.
options is an object which can
contain the following properties. Note that these properties
are exactly the same as the properties available in methods
DataSet.get and DataView.get.
| Name | Type | Description |
|---|---|---|
| convert | Object.<String, String> | An object containing field names as key, and data types as value. By default, the type of the properties of an item are left unchanged. When a field type is specified, this field in the items will be converted to the specified type. This can be used for example to convert ISO strings containing a date to a JavaScript Date object, or convert strings to numbers or vice versa. The available data types are listed in section Data Types. |
| fields | String[ ] |
An array with field names.
By default, all properties of the items are emitted.
When fields is defined, only the properties
whose name is specified in fields will be included
in the returned items.
|
| filter | function | Items can be filtered on specific properties by providing a filter function. A filter function is executed for each of the items in the DataSet, and is called with the item as parameter. The function must return a boolean. All items for which the filter function returns true will be emitted. See also section Data Filtering. |
Data of the DataView can be retrieved using the method get.
var items = view.get();
Data of a DataView can be filtered and formatted again, in exactly the same way as in a DataSet. See sections Data Filtering and Data Formatting for more information.
var items = view.get({
fields: ['id', 'score'],
filter: function (item) {
return (item.score > 50);
}
});
One can subscribe on changes in the DataView. Subscription works exactly the same as for DataSets. See the documentation on subscriptions in a DataSet for more information.
// create a DataSet and a view on the data set
var data = new vis.DataSet();
var view = new vis.DataView({
filter: function (item) {
return (item.group == 2);
}
});
// subscribe to any change in the DataView
view.subscribe('*', function (event, params, senderId) {
console.log('event:', event, 'params:', params, 'senderId:', senderId);
});
// add, update, and remove data in the DataSet...
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