I'm trying to stringify the mousewheel event using the following function. The function works fine in other instances, but in this instance I'm getting Maximum call stack size exceeded. How can I make it only return properties/methods to the nth level?
function cloneAsObject(obj) {
if (obj === null || !(obj instanceof Object)) {
return obj;
}
var temp = (obj instanceof Array) ? [] : {};
for (var key in obj) {
temp[key] = cloneAsObject(obj[key]);
}
return temp;
}
Edit: The original answer below leads to an error:
Uncaught TypeError: Converting circular structure to JSON
So the level of recursion is not the problem (as Alexandre Dupriez already commented). Here is a function that returns a simple string representation, ignoring nested objects and functions (see this answer Converting circular structure to JSON):
function simpleStringify (obj){
var simpleObject = {};
for (var prop in obj ){
/*if (!obj.hasOwnProperty(prop)){
continue;
}*/
if (typeof(obj[prop]) == 'object'){
continue;
}
if (typeof(obj[prop]) == 'function'){
continue;
}
simpleObject[prop] = obj[prop];
}
return JSON.stringify(simpleObject);
}
Original answer: Just count the recursion level with a second argument. For example:
function cloneAsObject(obj, level) {
if (level >= 100 || obj === null || !(obj instanceof Object)) {
return obj;
}
var temp = (obj instanceof Array) ? [] : {};
for (var key in obj) {
temp[key] = cloneAsObject(obj[key], level + 1);
}
return temp;
}
Related
I am studying Ceylon and have question about it metamodel. I want to create some create some base class 'DataContainer' which allow to instantiate immutable classes with build-in equals-hash implementation:
e.g. Identifier(125, "ab") == Identifier(125, "ab")
So base class should collect all shared non-variable values and use this information in 'hash' an 'equals' methods.
I have wrote this code:
shared abstract class DataContainer(ClassDeclaration declaration) {
value members = {
for (i in declaration.memberDeclarations<ValueDeclaration>())
if (!i.variable, i.name != "hash", i.name != "string") i
};
variable Integer? hashCode = null;
shared actual Boolean equals(Object that) {
if (is DataContainer that) {
for (item in members) {
value thisMember = item.memberGet(this);
value thatMember = item.memberGet(that);
if (exists thisMember, exists thatMember) {
if (thisMember != thatMember) { return false; }
} else if (thisMember exists != thatMember exists) { return false; }
}
return true;
}
return false;
}
shared actual Integer hash => hashCode else (hashCode = calculateHash());
Integer calculateHash() {
variable value result = 0;
for(i in members) {
if (exists member = i.memberGet(this)) {
result = result.xor(member.hash);
}
}
return result;
}
}
class Identifier(shared Integer? id, shared String? name) extends DataContainer(`class`) {}
The Identifier class is the client of DataContainer. I like this solution in whole but I have to pass 'class' into the super class constructor because if I use 'class' inside DataContainer it doesn't see any members of subclass.
How can I obtain actual list of extended class's members in base class methods?
Something like 'this' doesn't work...
I found solution thanks to guys from Ceylon community. The function classDeclaration(this) from ceylon.language.meta should be used instead of 'class'.
This is the final code:
shared abstract class DataContainer() {
variable Integer? _hash = null;
variable ValueDeclaration[]? _members = null;
shared actual Boolean equals(Object that) {
if (is DataContainer that) {
for (i in members) {
value thisMember = i.memberGet(this);
value thatMember = i.memberGet(that);
if (exists thisMember, exists thatMember) {
if (thisMember != thatMember) { return false; }
} else if (thisMember exists != thatMember exists) { return false; }
}
return true;
}
return false;
}
shared actual Integer hash => _hash else (_hash = calculateHash());
ValueDeclaration[] members => _members else (_members = [
for (i in classDeclaration(this).memberDeclarations<ValueDeclaration>())
if (!i.variable, i.name != "string", i.name != "hash") i
]);
Integer calculateHash() {
variable Integer result = 0;
for (i in members) {
if (exists member = i.memberGet(this)) {
result = result.xor(member.hash);
}
}
return result;
}
}
class Identifier(shared Integer? number, shared String? name) extends DataContainer() {}
Adding to Alexander's formidable answer, I took the liberty to implement a string function as well so you can just print(myObj) and it renders nicely:
shared default actual String string {
value s = StringBuilder();
s.append(type(this).declaration.name).append(" { ");
for (i in members) {
value m = i.memberGet(this);
s.append(i.name).append(":");
s.append(if(exists m) then m.string else "<null>");
}
return s.append(" }").string;
}
Beginner here,
I'm a bit lost with es6 set, map and generators.
How can I select an item in a map, then iterate backwards from that point on effectively? Preferably without going through the whole set/map.
let v = myMap.get('key')
so, from 'v' to the beginning of the map (backwards)?
thank you!
You can create a set of iteration helpers and then compound to create the effect you want:
/* iterTo iterates the iterable from the start and up to (inclusive) key is found.
The function "understands" the Map type when comparing keys as well as
any other iterables where the value itself is the key to match. */
function* iterTo(iterable, key) {
for(let i of iterable) {
yield i;
if((iterable instanceof Map && i[0] === key) || i === key)
return;
}
}
// Same as iterTo, but starts at the key and goes all the way to the end
function* iterFrom(iterable, key) {
let found = false;
for(let i of iterable) {
if(found = (found || (iterable instanceof Map && i[0] === key) || i === key))
yield i;
}
}
// reverseIter creates a reverse facade for iterable
function* reverseIter(iterable) {
let all = [...iterable];
for(let i = all.length; i--; )
yield all[i];
}
You can then use and compound like this:
let m = new Map();
m.set(1, 'a');
m.set(2, 'b');
m.set(3, 'c');
m.set(4, 'd');
m.set(5, 'e');
let s = new Set();
s.add(100);
s.add(200);
s.add(300);
s.add(400);
console.log(...iterTo(m, 3), ...iterFrom(m, 3));
console.log(...reverseIter(iterTo(m, 3)), ...reverseIter(iterFrom(m, 3)));
console.log(...reverseIter(iterTo(s, 200)));
What you probably want is a slice of the keys from the first element to the index of the key, reverse that, iterate over that and get the values from the map.
I am assuming your map is an object:
let keys = Object.keys(map);
return keys.slice(0, keys.indexOf('key')).map((k) => map[k]);
You don't really need a generator.
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;
}
Using org.as3commons.reflect I can look-up the class name, and instantiate a class at runtime. I also have (non-working) code which invokes a method. However, I really want to set a property value. I'm not sure if properties are realized as methods internally in Flex.
I have a Metadata class which stores 3 pieces of information: name, value, and type (all are strings). I want to be able to loop through an Array of Metadata objects and set the corresponding properties on the instantiated class.
package com.acme.reporting.builders
{
import com.acme.reporting.model.Metadata;
import mx.core.UIComponent;
import org.as3commons.reflect.ClassUtils;
import org.as3commons.reflect.MethodInvoker;
public class UIComponentBuilder implements IUIComponentBuilder
{
public function build(metadata:Array):UIComponent
{
var typeClass:Class = ClassUtils.forName(getTypeName(metadata));
var result:* = ClassUtils.newInstance(typeClass);
for each (var m:Metadata in metadata)
{
if (m.name == "type")
continue;
// Attempting to invoke as method,
// would really like the property though
var methodInvoker:MethodInvoker = new MethodInvoker();
methodInvoker.target = result;
methodInvoker.method = m.name;
methodInvoker.arguments = [m.value];
var returnValue:* = methodInvoker.invoke(); // Fails!
}
return result;
}
private static function getTypeName(metadata:Array):String
{
if (metadata == null || metadata.length == 0)
throw new ArgumentError("metadata is null or empty");
var typeName:String;
// Type is usually the first entry
if (metadata.length > 1 && metadata[0] != null && metadata[0].name == "type")
{
typeName = metadata[0].value;
}
else
{
var typeMetadata:Array = metadata.filter(
function(element:*, index:int, arr:Array):Boolean
{
return element.name == "type";
}
);
if (typeMetadata == null || typeMetadata.length != 1)
throw new ArgumentError("type entry not found in metadata");
typeName = typeMetadata[0].value;
}
if (typeName == null || typeName.length == 0)
throw new Error("typeName is null or blank");
return typeName;
}
}
}
Here's some usage code:
var metadata:Array = new Array();
metadata[0] = new Metadata("type", "mx.controls.Text", null);
metadata[1] = new Metadata("text", "Hello World!", null);
metadata[2] = new Metadata("x", "77", null);
metadata[3] = new Metadata("y", "593", null);
this.addChild(new UIComponentBuilder().build(metadata));
I realize that I have to declare a dummy variable of the type I was to instantiate, or use the -inculde compiler directive. An unfortunate drawback of Flex.
Also, right now there's code to account for typecasting the value to it's specified type.
Dynamic execution in AS3 is much simpler than in other languages. This code:
var methodInvoker:MethodInvoker = new MethodInvoker();
methodInvoker.target = result;
methodInvoker.method = m.name;
methodInvoker.arguments = [m.value];
var returnValue:* = methodInvoker.invoke(); // Fails!
can be simplified to this:
var returnValue:* = result[method](m.value);
EDIT:
Since it's a property, it would be done like this:
result[method] = m.value;
and there is no return value (well, you can call the getter again but it should just return m.value unless the setter/getter do something funky.
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;