I have the following code:
public fun findSomeLikeThis(): ArrayList<T>? {
val result = Db4o.objectContainer()!!.queryByExample<T>(this as T) as Collection<T>
if (result == null) return null
return ArrayList(result)
}
If I call this like:
var list : ArrayList<Person>? = p1.findSomeLikeThis()
for (p2 in list) {
p2.delete()
p2.commit()
}
It would give me the error:
For-loop range must have an 'iterator()' method
Am I missing something here?
Your ArrayList is of nullable type. So, you have to resolve this. There are several options:
for (p2 in list.orEmpty()) { ... }
or
list?.let {
for (p2 in it) {
}
}
or you can just return an empty list
public fun findSomeLikeThis(): List<T> //Do you need mutable ArrayList here?
= (Db4o.objectContainer()!!.queryByExample<T>(this as T) as Collection<T>)?.toList().orEmpty()
try
for(p2 in 0 until list.count()) {
...
...
}
I also face this problem when I loop on some thing it is not an array.
Example
fun maximum(prices: Array<Int>){
val sortedPrices = prices.sort()
for(price in sortedPrices){ // it will display for-loop range must have iterator here (because `prices.sort` don't return Unit not Array)
}
}
This is different case to this question but hope it help
This can also happen in Android when you read from shared preferences and are getting a (potentially) nullable iterable object back like StringSet. Even when you provide a default, the compiler is not able to determine that the returned value will never actually be null. The only way I've found around this is by asserting that the returned expression is not null using !! operator, like this:
val prefs = PreferenceManager.getDefaultSharedPreferences(appContext)
val searches = prefs.getStringSet("saved_searches", setOf())!!
for (search in searches){
...
}
Related
I have an object of $person as below:
$person = Person::where('id', $id)->first();
According to which $person exists or not I load other data:
if($person) {
$person->family_members = FamilyMemberController::FamilyMemberOf($person->id);
} else {
$person->family_members = [];
}
In the view file, I check the $person->family_members if not empty and exists to add a generated value :
if(!empty(array_filter($person->family_members))) {
// my code
}
But it throws an error:
array_filter(): Argument #1 ($array) must be of type array, Illuminate\Database\Eloquent\Collection given
I need to check this $person->family_members to make sure whether it's an array or a collection is not empty.
Writing code for if array do something if collection do something is the wrong way of implementation.
You can do two things.
use both returns as collection()
or either use both returns as an array[]
If collection
else {
$person->family_members = collect();
}
If array
use ->toArray() at the end of Eloquent. Check this answer
As well, I think you are confused with array_filter(). Maybe you are searching for in_array() or contains()
Use count method
if(count($person->family_members)>0){
//your code
}
We don't know your code, but given the error, it's safe to assume your method returns a Collection. You can see available methods in the docs. However, if you need it as array, all you need to do is call ->toArray() on the result Collection. Then you can use array_filter.
What about just doing
if(!$person->family_members){
// your code here
}
or
if($person->family_members){
// your code here
} else {
// code of "if it's empty" goes here
}
You can use the count() function to return a count of an index. ex
if(count($person->family_members)){
//do your true algo
}
Why you are using the empty method ?! Try this:
$person->family_members = $person ? FamilyMemberController::FamilyMemberOf($person->id) : null;
if($person->family_members){ // your code }
Try simple ways in Programming ;)
how can i check if any javaScript object's property exists and if it exists then it has a valid value?
actually,i am a beginner and trying to solve this-
Check if the second argument is truthy on all objects of the first argument(which is an array of objects).i.e.
check if the second argument exists in all the objects in first argument(an array) as a property.
if it exists, it should not be-
invalid, as age can't be 0
null
undefined
empty string('')
NaN
till now i have this-
function truthCheck(collection, pre) {
for(var i=0;i<collection.length;i++){
if(!(pre in collection[i])||collection[i]
[pre]===undefined||isNaN(collection[i]
[pre])||collection[i][pre]===""||
collection[i][pre]===null||collection[i]
[pre]===0)
{
return false;
}
}
return true;
}
i know this is not the best wayto solve .Is there a better way to do this?i don't like that long if statement in my code.i have seen other SO links-link1,link2 but none of them seemed to solve my query. any kind of help is highly appreciated.
P.S. this code is not working for some true cases even.
o = new Object();
o.prop = 'exist';
if(o.hasOwnProperty('prop')){
if(o['prop']){
alert('good value')
}
}
https://stackoverflow.com/a/6003920/1074179
this is what i was looking for and absolutely logical-
for(var i in array){
if((prop in array[i])&& Boolean(array[i][prop]))
{
//do something
}
}
the Boolean() function is something which made my day. Learn more at this link.
Look at the below example.
let the json object be
var a = { obj1:"a",obj2:"b"}
to check if an object exists,you can use hasOwnProperty() method.
a.hasOwnProperty("obj2") //this will return true
a.hasOwnProperty("obj3") // this will return false
to check the value of an object
if(a["obj1"] && a["obj1"]!="" && a["obj"]!=0){
//place your logic here
}
I have this line of code:
if ((self.datasource?.contains((self.textField?.text)!)) != nil) {
if let _ = self.placeHolderWhileSelecting {
// some code
}
Is there more clear way to check if the element contains in array? I have Bool returned by contains function, I dont want to check if this Bool is nil
Edit: the solution is to change array to non-optional type.
You can use the if let where construct. This code prevent crashes if self.datasource or self.textField are nil
if let
list = self.datasource,
elm = self.textField?.text,
_ = self.placeHolderWhileSelecting
where list.contains(elm) {
// your code
}
Another possible solution, using optional chaining to get to self.textField.text and assuming datasource remains optional.
if let unwrappedArray = self.datasource, let unwrappedString = self.textField?.text {
if unwrappedArray.contains(unwrappedString) {
// Some code
}
}
suppose you have an array with a number of strings in ActionScript3 and you want to test if a test string is "in" that array. "in" only works against the index with Arrays in AS3 (which is totally retardo if you ask me), though it does work with ojects, but we're not talking about objects.
Can someone improve (reduce) on this code I'm using now? I'm hoping to avoid defining a utility function - I'd like a nice elegant one-liner.
myArray.filter(function(item:*, i:int, a:Array) { return (item == testString); }).length
Since 0 == false we can use it in a test. Do note that testString's scope is defined in the containing function, encapsulated by the closure.
if (allowedProfiles.filter(function(item:*, i:int, a:Array) { return (item == name); }).length){ // yay! }
Use the Array.indexOf() method to see that the index of the string in the array is not -1 (not found):
var myArray:Array = ["hello", "world"];
trace(myArray.indexOf("hello")); // == 0;
trace(myArray.indexOf("goodbye")); // == -1
Why not just use indexOf()?
if(myArray.indexOf("testString") != -1) { // it's in there
Here's what I'm currently doing/trying to do to accomplish my goal. But it is not removing the "row" the way I would like it too.
So, I'm making an object, then pushing it into an array. And the adding to the array part works fine and just as I expect.
var nearProfileInfoObj:Object = new Object();
nearProfileInfoObj.type = "userInfo";
nearProfileInfoObj.dowhat = "add";
nearProfileInfoObj.userid = netConnection.nearID;
nearProfileInfoObj.username = username_input_txt.text;
nearProfileInfoObj.sex = sex_input_txt.selectedItem.toString();
nearProfileInfoObj.age = age_input_txt.selectedItem;
nearProfileInfoObj.location = location_input_txt.text;
nearProfileInfoObj.headline = headline_input_txt.text;
theArray.push(nearProfileInfoObj);
So after that later on I need to be able to remove that object from the array, and it's not working the way I'm expecting. I want to take a variable whoLeft and capture their ID and then look in the array for that particular ID in the userid part of the object and if its there DELETE that whole "row".
I know you can do a filter with an array collection but that doesnt actually delete it. I need to delete it because I may be adding the same value again later on.
whoLeft = theiruserIDVariable;
theArray.filter(userLeaving);
public function userLeaving(element:*, index:int, arr:Array):Boolean
{
if (element.userid == whoLeft)
{
return false;
}
else
{
return true;
}
}
But this doesnt seem to be deleting the whole row like it implies. Does anyone know what i'm doing wrong?
Instead of modifying the original array, the new filtered array is returned by the filter method. So you need to assign the returned array to theArray.
Try this
theArray = theArray.filter(userLeaving);
EDIT This turned out to be slower than for loop:
An alternative to the hand coded loop could be something like this:
theArray.every(searchAndDestroy);
public function searchAndDestroy(element:*, index:int, arr:Array):Boolean
{
if (element.userid == whoLeft)
{
arr.splice(index,1);
return false;
}
return true;
}
As far as I know, every() terminates the first time the test function returns false. So the question is: for a big list, which is faster, the for loop or the loop that every() does with the overhead of the test function call.
EDIT #2 But this was faster than a for loop for a test I ran on an array of a million Points:
for each(var element:Object in theArray)
{
if (element.userid==whoLeft)
{
theArray.splice(theArray.indexOf(element),1);
break;
}
}
I think this is what you're looking for:
for(var i:uint = 0, len:uint = theArray.length; i<len; i++)
{
if(thisArray[i].id == whoLeft.id)
{
thisArray.splice(i, 1);
break;
}
}
However, do you really need it in an Array because you could always use a Dictionary which would mean accessing it by id which would be a lot simpler to remove.