Servis-Rhino 4211B Guia do Utilizador descarregar pdf (Página 200)

• getIdentity

• queryEngine

• transaction

• getChildren

• getMetadata

The query method is very interesting. It can be used to query a store which returns an array of

objects that matched the query. The return is actually a Dojo NodeList. This returned array has a

number of methods on it including:

• forEach()

• map()

• filter()

• length

The query expression for the query is an object which has properties corresponding to the property

being sought. For example:

myStore.query({name: "Neil"})

will return all the objects in the store which have a name property equal to "Neil". To return all

items in the list, pass in an empty object ({}). If the parameter to query is a function then the query

will pass the function each item in the store and the result will be only those items that pass a test.

The second parameter to query is an object with properties as follows:

• start – Starting offset

• count – The number of objects to return

• sort – An array of objects where each object is a definition of how the sort is to be

performed. An instance of one of these objects will contain the following properties:

◦ attribute – The name of the attribute to sort upon

◦ descending – A boolean indicating whether we want ascending or descending sorting

It is possible to write our own function to perform the queryEngine task. The queryEngine

property of a store must be a function that takes the same parameters as the query. Your own

function does not do the work immediately. Instead, what it does is return a function which takes

an array as input and performs this specialized query.

The result from the query includes a method called:

forEach(function(entry) { … } )

which allows us to execute a function for each entry returned from the query.

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