dojo
Version:
Dojo core is a powerful, lightweight library that makes common tasks quicker and easier. Animate elements, manipulate the DOM, and query with easy CSS syntax, all without sacrificing performance.
197 lines (186 loc) • 7.21 kB
JavaScript
define(["../_base/kernel", "../_base/lang", "../when", "../_base/array" /*=====, "./api/Store" =====*/
], function(kernel, lang, when, array /*=====, Store =====*/){
// module:
// dojo/store/Observable
var Observable = function(/*Store*/ store){
// summary:
// The Observable store wrapper takes a store and sets an observe method on query()
// results that can be used to monitor results for changes.
//
// description:
// Observable wraps an existing store so that notifications can be made when a query
// is performed.
//
// example:
// Create a Memory store that returns an observable query, and then log some
// information about that query.
//
// | var store = Observable(new Memory({
// | data: [
// | {id: 1, name: "one", prime: false},
// | {id: 2, name: "two", even: true, prime: true},
// | {id: 3, name: "three", prime: true},
// | {id: 4, name: "four", even: true, prime: false},
// | {id: 5, name: "five", prime: true}
// | ]
// | }));
// | var changes = [], results = store.query({ prime: true });
// | var observer = results.observe(function(object, previousIndex, newIndex){
// | changes.push({previousIndex:previousIndex, newIndex:newIndex, object:object});
// | });
//
// See the Observable tests for more information.
var undef, queryUpdaters = [], revision = 0;
// a Comet driven store could directly call notify to notify observers when data has
// changed on the backend
// create a new instance
store = lang.delegate(store);
store.notify = function(object, existingId){
revision++;
var updaters = queryUpdaters.slice();
for(var i = 0, l = updaters.length; i < l; i++){
updaters[i](object, existingId);
}
};
var originalQuery = store.query;
store.query = function(query, options){
options = options || {};
var results = originalQuery.apply(this, arguments);
if(results && results.forEach){
var nonPagedOptions = lang.mixin({}, options);
delete nonPagedOptions.start;
delete nonPagedOptions.count;
var queryExecutor = store.queryEngine && store.queryEngine(query, nonPagedOptions);
var queryRevision = revision;
var listeners = [], queryUpdater;
results.observe = function(listener, includeObjectUpdates){
if(listeners.push(listener) == 1){
// first listener was added, create the query checker and updater
queryUpdaters.push(queryUpdater = function(changed, existingId){
when(results, function(resultsArray){
var atEnd = resultsArray.length != options.count;
var i, l, listener;
if(++queryRevision != revision){
throw new Error("Query is out of date, you must observe() the query prior to any data modifications");
}
var removedObject, removedFrom = -1, insertedInto = -1;
if(existingId !== undef){
// remove the old one
var filteredArray = [].concat(resultsArray);
if(queryExecutor && !changed){
filteredArray = queryExecutor(resultsArray);
}
for(i = 0, l = resultsArray.length; i < l; i++){
var object = resultsArray[i];
if(store.getIdentity(object) == existingId){
if(filteredArray.indexOf(object)<0) continue;
removedObject = object;
removedFrom = i;
if(queryExecutor || !changed){// if it was changed and we don't have a queryExecutor, we shouldn't remove it because updated objects would be eliminated
resultsArray.splice(i, 1);
}
break;
}
}
}
if(queryExecutor){
// add the new one
if(changed &&
// if a matches function exists, use that (probably more efficient)
(queryExecutor.matches ? queryExecutor.matches(changed) : queryExecutor([changed]).length)){
var firstInsertedInto = removedFrom > -1 ?
removedFrom : // put back in the original slot so it doesn't move unless it needs to (relying on a stable sort below)
resultsArray.length;
resultsArray.splice(firstInsertedInto, 0, changed); // add the new item
insertedInto = array.indexOf(queryExecutor(resultsArray), changed); // sort it
// we now need to push the change back into the original results array
resultsArray.splice(firstInsertedInto, 1); // remove the inserted item from the previous index
if((options.start && insertedInto == 0) ||
(!atEnd && insertedInto == resultsArray.length)){
// if it is at the end of the page, assume it goes into the prev or next page
insertedInto = -1;
}else{
resultsArray.splice(insertedInto, 0, changed); // and insert into the results array with the correct index
}
}
}else if(changed){
// we don't have a queryEngine, so we can't provide any information
// about where it was inserted or moved to. If it is an update, we leave it's position alone, other we at least indicate a new object
if(existingId !== undef){
// an update, keep the index the same
insertedInto = removedFrom;
}else if(!options.start){
// a new object
insertedInto = store.defaultIndex || 0;
resultsArray.splice(insertedInto, 0, changed);
}
}
if((removedFrom > -1 || insertedInto > -1) &&
(includeObjectUpdates || !queryExecutor || (removedFrom != insertedInto))){
var copyListeners = listeners.slice();
for(i = 0;listener = copyListeners[i]; i++){
listener(changed || removedObject, removedFrom, insertedInto);
}
}
});
});
}
var handle = {};
// TODO: Remove cancel in 2.0.
handle.remove = handle.cancel = function(){
// remove this listener
var index = array.indexOf(listeners, listener);
if(index > -1){ // check to make sure we haven't already called cancel
listeners.splice(index, 1);
if(!listeners.length){
// no more listeners, remove the query updater too
queryUpdaters.splice(array.indexOf(queryUpdaters, queryUpdater), 1);
}
}
};
return handle;
};
}
return results;
};
var inMethod;
function whenFinished(method, action){
var original = store[method];
if(original){
store[method] = function(value){
var originalId;
if(method === 'put'){
originalId = store.getIdentity(value);
}
if(inMethod){
// if one method calls another (like add() calling put()) we don't want two events
return original.apply(this, arguments);
}
inMethod = true;
try{
var results = original.apply(this, arguments);
when(results, function(results){
action((typeof results == "object" && results) || value, originalId);
});
return results;
}finally{
inMethod = false;
}
};
}
}
// monitor for updates by listening to these methods
whenFinished("put", function(object, originalId){
store.notify(object, originalId);
});
whenFinished("add", function(object){
store.notify(object);
});
whenFinished("remove", function(id){
store.notify(undefined, id);
});
return store;
};
lang.setObject("dojo.store.Observable", Observable);
return Observable;
});