I have seen similar questions but I think my scenario is a bit different. Say I define a collection like this:
MyCol = new Meteor.Collection("myCol"
and I want to get a reference to 'MyCol' using the string 'myCol' - I have created the function below which seems to work:
function GetCollectionObject(name) {
for(var key in window) {
var value = window[key];
if (value instanceof Meteor.Collection) {
if (value._name == name) {
return value;
break;
}
}
}
return null;
}
Is this the only/best/most efficient way to do this?
Why don't you store your collections in a dictionary? It's way more efficient.
Dogs = new Meteor.Collection('dogs');
Cats = new Meteor.Collection('cats');
Alpacas = new Meteor.Collection('alpacas');
MyCollections = {
dogs: Dogs,
cats: Cats,
alpacas: Alpacas,
};
...
MyCollections['dogs'].doSomething();
Related
I am using the following code to first check if a string is located somewhere within a column in my database. If it is, I am then needing to check if a few additional criteria are met by looking at different parts of the database (can be seen in the code below). I am not sure if this is an efficient method for doing this or if there is a much simpler way:
(from my Controller)
[HttpPost]
public ActionResult Index(FormCollection sampleKey)
{
string code = sampleKey["sampleCode"];
ViewBag.code = code;
// Need to check if this code is active
var order = db.Orders.SingleOrDefault(
o => o.OrderCode == code
&& o.Active == true);
if (order == null)
{
//Invalid
}
else
{
var orderIdent = db.OrderDetails.SingleOrDefault(
p => p.OrderDetailId == order.OrderId);
var barIdent = db.Drink.SingleOrDefault(
q => q.EstablishmentsID == orderIdent.DrinksId);
var barName = db.Establishment.SingleOrDefault(
r => r.EstablishmentsId == barIdent.EstablishmentsID);
ViewBag.barId = barName.name;
ViewBag.sample = order.Email;
var custProfile = CustomProfile.GetUserProfile();
if (custProfile.OwnedBar != barName.name)
{
//Not a match
}
else
{
//Match
}
}
return View();
}
Is this something to worry about? Is there a more efficient way of performing the actions that I am currently performing? Should I change the first table that is referenced to include data from the table I ultimately compare it to to avoid what seems to be an inefficient way of comparing information from different tables?
You should check the SQL query that gets generated. You can do that by e.g. outputting the queries to the console, which is done by setting db.Log = Console.Out;. There should be a similar method to output to the web page in your case. The lazy nature of LINQ makes things difficult to predict.
Other than that, you could make your life much easier if you create foreign key relationships between your tables, i.e. OrderDetails has Orders.OrderId as a FK. This will allow Entity Framework to generate navigational properties for your database. With them your code would look like this:
[HttpPost]
public ActionResult Index(FormCollection sampleKey)
{
string code = sampleKey["sampleCode"];
var detail = db.Orders.Where(o => o.OrderCode == code && o.Active == true)
.Select(o => new {
OrderCode = o.OrderCode,
BarId = o.Drink.Establishment.Select(n => n.name),
Sample = o.Email
})
.SingleOrDefault();
if (detail != null)
{
ViewBag.code = detail.OrderCode;
ViewBag.barId = detail.BarId;
ViewBag.sample = detail.Sample;
var custProfile = CustomProfile.GetUserProfile();
if (custProfile.OwnedBar == detail.BarId)
{
//Match
}
else
{
//Not a match
}
}
else
{
//Invalid
}
return View();
}
My goal is to create a generic function that selects a value in a combobox accoring to a value.
(My comoBox holds arrayCollection as dataProvider.)
The difficulty is infact to get a propertyname in runtime mode
public function selectComboByLabel(combo:ComboBox , propetryName:String, value:String):void {
var dp:ArrayCollection = combo.dataProvider as ArrayCollection;
for (var i:int=0;i<dp.length;i++) {
if (dp.getItemAt(i).propertyName==value) {
combo.selectedIndex = i;
return;
}
}
}
the line if (dp.getItemAt(i).propertyName==value)
is of course incorrect.
It should be arther something like: dp.getItemAt(i).getPropertyByName(propertyName)
Any clue on how to that ?
Don't use Object Property notation. Do this:
dp.getItemAt(i)[propertyName]
In addition to what Flextras said, you could also redo your for loop to make it easier to read:
for each(var item:Object in dp) {
if(item[propertyName] == value) {
combo.selectedItem = item;
return;
}
}
I have an array of objects. Each object has a property called name. I want to efficiently remove an object with a particular name from the array. Is this the BEST way?
private function RemoveSpoke(Name:String):void {
var Temp:Array=new Array;
for each (var S:Object in Spokes) {
if (S.Name!=Name) {
Temp.push(S);
}
}
Spokes=Temp;
}
If you are willing to spend some memory on a lookup table this will be pretty fast:
private function remove( data:Array, objectTable:Object, name:String):void {
var index:int = data.indexOf( objectTable[name] );
objectTable[name] = null;
data.splice( index, 1 );
}
The test for this looks like this:
private function test():void{
var lookup:Object = {};
var Spokes:Array = [];
for ( var i:int = 0; i < 1000; i++ )
{
var obj:Object = { name: (Math.random()*0xffffff).toString(16), someOtherProperty:"blah" };
if ( lookup[ obj.name ] == null )
{
lookup[ obj.name ] = obj;
Spokes.push( obj );
}
}
var t:int = getTimer();
for ( var i:int = 0; i < 500; i++ )
{
var test:Object = Spokes[int(Math.random()*Spokes.length)];
remove(Spokes,lookup,test.name)
}
trace( getTimer() - t );
}
myArray.splice(myArray.indexOf(myInstance), 1);
The fastest way will be this:
function remove(array: Array, name: String): void {
var n: int = array.length
while(--n > -1) {
if(name == array[n].name) {
array.splice(n, 1)
return
}
}
}
remove([{name: "hi"}], "hi")
You can also remove the return statement if you want to get rid of all alements that match the given predicate.
I don't have data to back it up but my guess is that array.filter might be the fastest.
In general you should prefer the old for-loop over "for each" and "for each in" and use Vector if your elements are of the same type. If performance is really important you should consider using a linked list.
Check out Grant Skinners slides http://gskinner.com/talks/quick/ and Jackson Dunstan's Blog for more infos about optimization.
If you don't mind using the ArrayCollection, which is a wrapper for the Array class, you could do something like this:
private function RemoveSpoke(Name:String, Spokes:Array):Array{
var ac:ArrayCollection = new ArrayCollection(Spokes);
for (var i:int=0, imax:int=ac.length; i<imax; i++) {
if (Spokes[i].hasOwnProperty("Name") && Spokes[i].Name === Name) {
ac.removeItemAt(i);
return ac.source;
}
}
return ac.source;
}
You could also use ArrayCollection with a filterFunction to get a view into the same Array object
Perhaps this technique (optimized splice method by CJ's) will further improve the one proposed by Quasimondo:
http://cjcat.blogspot.com/2010/05/stardust-v11-with-fast-array-splicing_21.html
Here's an efficient function in terms of reusability, allowing you to do more than remove the element. It returns the index, or -1 if not found.
function searchByProp(arr:Array, prop:String, value:Object): int
{
var item:Object;
var n: int = arr.length;
for(var i:int=n;i>0;i--)
{
item = arr[i-1];
if(item.hasOwnProperty(prop))
if( value == item[prop] )
return i-1;
}
return -1;
}
OK, I am sorting an XMLListCollection in alphabetical order. I have one issue though. If the value is "ALL" I want it to be first in the list. In most cases this happens already but values that are numbers are being sorted before "ALL". I want "ALL" to always be the first selection in my dataProvider and then the rest alphabetical.
So I am trying to write my own sort function. Is there a way I can check if one of the values is all, and if not tell it to do the regular compare on the values?
Here is what I have:
function myCompare(a:Object, b:Object, fields:Array = null):int
{
if(String(a).toLowerCase() == 'all')
{
return -1;
}
else
if(String(b).toLowerCase() == 'all')
{
return 1;
}
// NEED to return default comparison results here?
}
//------------------------------
var sort:Sort = new Sort();
sort.compareFunction = myCompare;
Is there a solution for what I am trying to do?
The solution from John Isaacks is awesome, but he forgot about "fields" variable and his example doesn't work for more complicated objects (other than Strings)
Example:
// collection with custom objects. We want to sort them on "value" property
// var item:CustomObject = new CustomObject();
// item.name = 'Test';
// item.value = 'Simple Value';
var collection:ArrayCollection = new ArrayCollection();
var s:Sort = new Sort();
s.fields = [new SortField("value")];
s.compareFunction = myCompare;
collection.sort = s;
collection.refresh();
private function myCompare(a:Object, b:Object, fields:Array = null):int
{
if(String((a as CustomObject).value).toLowerCase() == 'all')
{
return -1;
}
else if(String((b as CustomObject).value).toLowerCase() == 'all')
{
return 1;
}
// NEED to return default comparison results here?
var s:Sort = new Sort();
s.fields = fields;
var f:Function = s.compareFunction;
return f.call(null,a,b,fields);
}
Well I tried something out, and I am really surprised it actually worked, but here is what I did.
The Sort class has a private function called internalCompare. Since it is private you cannot call it. BUT there is a getter function called compareFunction, and if no compare function is defined it returns a reference to the internalCompare function. So what I did was get this reference and then call it.
private function myCompare(a:Object, b:Object, fields:Array = null):int
{
if(String(a).toLowerCase() == 'all')
{
return -1;
}
else if(String(b).toLowerCase() == 'all')
{
return 1;
}
// NEED to return default comparison results here?
var s:Sort = new Sort();
var f:Function = s.compareFunction;
return f.call(null,a,b,fields);
}
Thanks guys, this helped a lot. In our case, we needed all empty rows (in a DataGrid) on the bottom. All non-empty rows should be sorted normally. Our row data is all dynamic Objects (converted from JSON) -- the call to ValidationHelper.hasData() simply checks if the row is empty. For some reason the fields sometimes contain the dataField String value instead of SortFields, hence the check before setting the 'fields' property:
private function compareEmptyAlwaysLast(a:Object, b:Object, fields:Array = null):int {
var result:int;
if (!ValidationHelper.hasData(a)) {
result = 1;
} else if (!ValidationHelper.hasData(b)) {
result = -1;
} else {
if (fields && fields.length > 0 && fields[0] is SortField) {
STATIC_SORT.fields = fields;
}
var f:Function = STATIC_SORT.compareFunction;
result = f.call(null,a,b,fields);
}
return result;
}
I didn't find these approaches to work for my situation, which was to alphabetize a list of Strings and then append a 'Create new...' item at the end of the list.
The way I handled things is a little inelegant, but reliable.
I sorted my ArrayCollection of Strings, called orgNameList, with an alpha sort, like so:
var alphaSort:Sort = new Sort();
alphaSort.fields = [new SortField(null, true)];
orgNameList.sort = alphaSort;
orgNameList.refresh();
Then I copied the elements of the sorted list into a new ArrayCollection, called customerDataList. The result being that the new ArrayCollection of elements are in alphabetical order, but are not under the influence of a Sort object. So, adding a new element will add it to the end of the ArrayCollection. Likewise, adding an item to a particular index in the ArrayCollection will also work as expected.
for each(var org:String in orgNameList)
{
customerDataList.addItem(org);
}
Then I just tacked on the 'Create new...' item, like this:
if(userIsAllowedToCreateNewCustomer)
{
customerDataList.addItem(CREATE_NEW);
customerDataList.refresh();
}
I want to check in my function if a passed argument of type object is empty or not. Sometimes it is empty but still not null thus I can not rely on null condition. Is there some property like 'length'/'size' for flex objects which I can use here.
Please help.
Thanks in advance.
If you mean if an Object has no properties:
var isEmpty:Boolean = true;
for (var n in obj) { isEmpty = false; break; }
This is some serious hack but you can use:
Object.prototype.isEmpty = function():Boolean {
for(var i in this)
if(i != "isEmpty")
return false
return true
}
var p = {};
trace(p.isEmpty()); // true
var p2 = {a:1}
trace(p2.isEmpty()); // false
You can also try:
ObjectUtil.getClassInfo(obj).properties.length > 0
The good thing about it is that getClassInfo gives you much more info about the object, eg. you get the names of all the properties in the object, which might come in handy.
If object containes some 'text' but as3 doesn't recognize it as a String, convert it to string and check if it's empty.
var checkObject:String = myObject;
if(checkObject == '')
{
trace('object is empty');
}
Depends on what your object is, or rather what you expect it to have. For example if your object is supposed to contain some property called name that you are looking for, you might do
if(objSomeItem == null || objSomeItem.name == null || objSomeItem.name.length == 0)
{
trace("object is empty");
}
or if your object is actually supposed to be something else, like an array you could do
var arySomeItems = objSomeItem as Array;
if(objSomeItem == null || arySomeItems == null || arySomeItems.length == 0)
{
trace("object is empty");
}
You could also use other ways through reflection, such as ObjectUtil.getClassInfo, then enumerate through the properties to check for set values.... this class help:
import flash.utils.describeType;
import flash.utils.getDefinitionByName;
public class ReflectionUtils
{
/** Returns an Array of All Properties of the supplied object */
public static function GetVariableNames(objItem:Object):Array
{
var xmlPropsList:XMLList = describeType(objItem)..variable;
var aryVariables:Array = new Array();
if (xmlPropsList != null)
{
for (var i:int; i < xmlPropsList.length(); i++)
{
aryVariables.push(xmlPropsList[i].#name);
}
}
return aryVariables;
}
/** Returns the Strongly Typed class of the specified library item */
public static function GetClassByName($sLinkageName:String):Class
{
var tObject:Class = getDefinitionByName($sLinkageName) as Class;
return tObject;
}
/** Constructs an instance of the speicified library item */
public static function ConstructClassByName($sLinkageName:String):Object
{
var tObject:Class = GetClassByName($sLinkageName);
//trace("Found Class: " + tMCDefinition);
var objItem:* = new tObject();
return objItem;
}
public static function DumpObject(sItemName:String, objItem:Object):void
{
trace("*********** Object Dump: " + sItemName + " ***************");
for (var sKey:String in objItem)
{
trace(" " + sKey +": " + objItem[sKey]);
}
}
//}
}
Another thing to note is you can use a simple for loop to check through an objects properties, thats what this dumpobject function is doing.
You can directly check it as follow,
var obj:Object = new Object();
if(obj == null)
{
//Do something
}
I stole this from a similar question relating to JS. It requires FP 11+ or a JSON.as library.
function isEmptyObject(obj){
return JSON.stringify(obj) === '{}';
}
can use use the hasProperty method to check for length
var i:int = myObject.hasProperty("length") ? myObject.length: 0;