use map function on condition in kotlin - kotlin

I have a list of items and I want to edit its values before using it. I am using the map function to update each item in it. But the catch here is, I want to only update the items when the list size is 1. I want to return the list as it is if the size is larger than 1. How can I achieve this?
myList.map {
if(resources.getBoolean(R.bool.is_tablet) && it.itemList.size<6 && it.layerType == DOUBLE_LIST) {
it.layerType = SINGLE_LIST_AUTO
it.itemList.forEach {sectionItem->
sectionItem.layerType = SINGLE_LIST_AUTO
}
it
}else{
it
}
}

You can try using filter before map:
.filter { it.itemList.size == 1 }

I am assuming you want to modify the items in your list only if some conditions are met else return the same list unmodified.
You can consider using takeIf { } for this scenario if you desire to add some syntactic sugar
fun updateItemsInMyList(myList:List<SomeClass>): List<SomeClass> {
return myList
.takeIf {
// condition to modify items in your list
it.size > 1 && otherConditions
}
?.apply {
//update your items inside the list
}
?: myList // return the unmodified list if conditions are not met
}

If I understand your question correctly, you want to check if myList contains only one value else, you want update the values and return it. You could do something along the following lines,
myList.singleOrNull ?: myList.map {
if(resources.getBoolean(R.bool.is_tablet) && it.itemList.size<6 && it.layerType == DOUBLE_LIST) {
it.layerType = SINGLE_LIST_AUTO
it.itemList.forEach {sectionItem->
sectionItem.layerType = SINGLE_LIST_AUTO
}
it
}else{
it
}
}
return myList
Basically, check if there's only a single value in the list, if so, then return the value. In the case that there isn't (you get null), then you can map the value.

Related

Nested Loop select the minimum defined value asp.net

I have a list of states, which are defined to be ordered by min to max. the sequence is the following:
Cancelled - complete - draft - reservation - reserved - ordered - confirmed
So the cancelled is the minimum state, and confirmed is the maximum state. I may have different instances with different states, so I use a for-each loop to run through all states, and select the minimum state present in the loop.
That is: if in a list I have states [complete, reserved, draft, ordered] I need to check all the values and select complete -as it appears to be the minimum state. OR
if I have [reserved, confirmed, ordered, draft, cancelled, confirmed, confirmed] I need to select the cancelled value, as it appears to be the minimum.
I am doing the following check, but it does not seem to be working:
string globstatus = " ";
foreach (var currentstatus in list)
{
if (currentstatus == "cancelled")
{
globstatus = "cancelled";
}
else
{
if (globstatus == "cancelled")
{
return globstatus;
}
else
{
if (currentstatus == "complete")
{
globstatus = "complete";
}
else
{
if (globstatus == "complete")
{
return globstatus;
}
else
{
if (currentstatus == "draft")
{
globstatus = "draft";
}
else
{
if (globstatus == "reservation")
{
return globstatus;
}
else
{
if (currentstatus == "reserved")
{
globstatus = "reserved";
}
else
{
if (globstatus == "ordered")
{
return globstatus;
}
else
{
if (currentstatus == "confirmed")
{
globstatus = "confirmed";
}
else
{
return currentstatus;
}
}
}
}
}
}
}
}
}
}
return globstatus;
What can be the best solution to achieve the desired behavior?
I find a rule of thumb helpful that if I need more than three levels of braces, I need to rethink my code. It's hard to follow, easy to make mistakes, and a nightmare to debug. I suggest that applies here - trying to follow the flow of what all those nested if..else statements is extremely difficult.
Using Enum
My preferred solution is to achieve this using an Enum, e.g.:
var list = new List<Status>
{
Status.Complete,
Status.Draft,
Status.Draft,
Status.Confirmed
};
var minStatus = (Status)list.Select(l => (int)l).Min();
// minStatus = Status.Complete
public enum Status
{
Cancelled,
Complete,
Draft,
Reservation,
Reserved,
Ordered,
Confirmed
}
How it works: by default Enums give each value a zero-based integer, i.e. Cancelled = 0, Complete = 1 and so on. You can override this with your own values if you wish (e.g. 1/2/4/8/16 if you want to combine multiple values).
I recommend using Enum types for things like this, rather than strings. It helps avoid typos, gives someone else looking at your code a clear understanding of how your program works and its flow, and represents hierarchy in a way in which simple strings don't. (For example - does 'complete' come before or after 'draft'? Without context, I imagine most people would say after, but in this case it comes before - that is much more obvious when using an Enum.)
Parse strings to Enum
However if the statuses have to be strings, you could parse them into an enum like so:
var stringList = new List<string>
{
"complete",
"draft",
"draft",
"confirmed",
"this will be ignored"
};
var statusList = new List<int>();
foreach (var str in stringList)
{
if(Enum.TryParse(typeof(Status), str, ignoreCase: true, out object? parsed) && parsed is Status status)
{
statusList.Add((int)status);
}
}
var minStatus = (Status)statusList.Min();
// minStatus = Status.Complete
However, if it's possible to refactor your code to use the Enum in the first place, that would be a better solution, and much quicker as parsing strings has an overhead that would be good to avoid.

How to merge collections based on object's particular key's value match in laravel6?

I have three collections.
SalaryCollection
BonusCollection
Deduction Collection
All of them have date which is common in some of them.
I want to merge these three into one collection in a way that object with same date in three becomes one as a result.
Something like this:
#items:array:2[
0=>{
+"date":"1-2020"
+"salaries":36500.0
+"deductions":1500.0
+"bonuses":7000.0
}
1=>{
+"date":"2-2020"
+"salaries":20000.0
+"deductions":1000.0
+"bonuses":5000.0
}
]
How can i do it?
I am not sure if this is the best way to do it but this is how i made it worked.
$salaryCollection = $salaryCollection->map(function ($item, $key) use ($bonusCollection) {
$single_bonus = $bonusCollection->where('date', $item->date);
if (!$single_bonus->isEmpty()) {
return collect($item)->put('bonuses', $single_bonus->first()->bonuses);
} else {
return collect($item)->put('bonuses', 0);
}
});
$salaryCollection = $salaryCollection->map(function ($item, $key) use ($deductionCollection) {
$single_deduction = $deductionCollection->where('date', $item['date']);
if (!$single_deduction->isEmpty()) {
return collect($item)->put('deductions', $single_deduction->first()->deductions);
} else {
return collect($item)->put('deductions', 0);
}
});

Is there a way to merge filter and map into single operation in Kotlin?

The below code will look for "=" and then split them. If there's no "=", filter them away first
myPairStr.asSequence()
.filter { it.contains("=") }
.map { it.split("=") }
However seeing that we have both
.filter { it.contains("=") }
.map { it.split("=") }
Wonder if there's a single operation that could combine the operation instead of doing it separately?
You can use mapNotNull instead of map.
myPairStr.asSequence().mapNotNull { it.split("=").takeIf { it.size >= 2 } }
The takeIf function will return null if the size of the list returned by split method is 1 i.e. if = is not present in the string. And mapNotNull will take only non null values and put them in the list(which is finally returned).
In your case, this solution will work. In other scenarios, the implementation(to merge filter & map) may be different.
I see your point and under the hood split is also doing an indexOf-check to get the appropriate parts.
I do not know of any such function supporting both operations in a single one, even though such a function would basically just be similar to what we have already for the private fun split-implementation.
So if you really want both in one step (and require that functionality more often), you may want to implement your own splitOrNull-function, basically copying the current (private) split-implementation and adapting mainly 3 parts of it (the return type List<String>?, a condition if indexOf delivers a -1, we just return null; and some default values to make it easily usable (ignoreCase=false, limit=0); marked the changes with // added or // changed):
fun CharSequence.splitOrNull(delimiter: String, ignoreCase: Boolean = false, limit: Int = 0): List<String>? { // changed
require(limit >= 0, { "Limit must be non-negative, but was $limit." })
var currentOffset = 0
var nextIndex = indexOf(delimiter, currentOffset, ignoreCase)
if (nextIndex == -1 || limit == 1) {
if (currentOffset == 0 && nextIndex == -1) // added
return null // added
return listOf(this.toString())
}
val isLimited = limit > 0
val result = ArrayList<String>(if (isLimited) limit.coerceAtMost(10) else 10)
do {
result.add(substring(currentOffset, nextIndex))
currentOffset = nextIndex + delimiter.length
// Do not search for next occurrence if we're reaching limit
if (isLimited && result.size == limit - 1) break
nextIndex = indexOf(delimiter, currentOffset, ignoreCase)
} while (nextIndex != -1)
result.add(substring(currentOffset, length))
return result
}
Having such a function in place you can then summarize both, the contains/indexOf and the split, into one call:
myPairStr.asSequence()
.mapNotNull {
it.splitOrNull("=") // or: it.splitOrNull("=", limit = 2)
}
Otherwise your current approach is already good enough. A variation of it would just be to check the size of the split after splitting it (basically removing the need to write contains('=') and just checking the expected size, e.g.:
myPairStr.asSequence()
.map { it.split('=') }
.filter { it.size > 1 }
If you want to split a $key=$value-formats, where value actually could contain additional =, you may want to use the following instead:
myPairStr.asSequence()
.map { it.split('=', limit = 2) }
.filter { it.size > 1 }
// .associate { (key, value) -> key to value }

Filtering data out of a collection with specific string

I would like to receive only data which does not contain some specific strings.
What I have is this code:
#GET
#Path("getParticipants")
#Produces(MediaType.APPLICATION_JSON)
fun getParticipants(): Map<String, List<String>> {
val (nodeInfo, nodeUpdates) = rpcOps.networkMapFeed()
nodeUpdates.notUsed()
return mapOf("getParticipants" to nodeInfo
.map { it.legalIdentities.first().toString() }
.filter { it != myLegalName && it !in NOTARY_NAMES })
}
While running this code above I recive this:
0 "C=GB,L=London,O=UserA"
1 "C=GB,L=London,O=Controller"
2 "C=US,L=New York,O=UserB"
myLegalName is = "UserA"
NOTARY_NAMES is = "Controller"
What I would like to achive is, that the getParticipants retrieves me only the rows which are NOT CONTAINING UserA ("myLegalName") and NOT CONTAINING Controller ("NOTARY_NAMES"), so in this case only "C=US,L=New York,O=UserB".
Based upon your stated output, your predicate after substituting for your result values looks like this...
"C=GB,L=London,O=UserA" != "UserA" && "C=GB,L=London,O=UserA" !in "Controller"
// or, after using information from your comments
"C=GB,L=London,O=UserA" != "UserA" && "C=GB,L=London,O=UserA" !in listOf("Controller","NetworkSErvice")
... and of course neither filters out what you want.
If some other field besides legalIdentities.first() contains the information you want, then filter on that (and call filter before map)...
.filter { it.someOtherField() != myLegalName &&
it.someOtherField() !in NOTARY_NAMES } //then...
.map { it.legalIdentities.first().toString() }
Otherwise, parse .legalIdentities.first() to get the "O" member of the string and filter on that.

Comparing DropDownLists

I'm having a page that contains several dropdownlists, all filled with the same values. I would like to compare them on the client as well as on the server side.
The problem is though, that the dropdownlists are generated dynamically because their quantity can vary.
Client side comparing:
<script type="text/javascript">
function CompareSelectedValues(dropDown1ID, dropDown2ID) {
var DropDownList1 = document.getElementById(dropDown1ID);
var DropDownList2 = document.getElementById(dropDown2ID);
if (DropDownList1.selectedIndex != -1 && DropDownList2.selectedIndex != -1) {
if (DropDownList1.options[DropDownList1.selectedIndex].value != DropDownList2.options[DropDownList2.selectedIndex].value)
alert('not same');
}
}
</script>
Classic server side comparing with C#:
private bool AreDropDownListValuesEqual(DropDownList ddlist1, DropDownList ddlist2)
{
// Check for invalid input or different number of items for early return
if (ddlist1 == null || ddlist2 == null || ddlist1.Items.Count != ddlist2.Items.Count)
{
return false;
}
// Check items one by one. We need a nested loop because the list could be sorted differently while having the same values!
foreach (ListItem outerItem in ddlist1.Items)
{
bool hasMatch = false;
foreach (ListItem innerItem in ddlist2.Items)
{
if (innerItem.Value == outerItem.Value && innerItem.Text == outerItem.Text)
{
hasMatch = true;
break;
}
}
if (!hasMatch)
{
return false;
}
}
// All items from ddlist1 had a match in ddlist2 and we know that the number of items is equal, so the 2 dropdownlist are matching!
return true;
}
What kind of comparison do you need? If you don't keep them in a List and that list in Session, you can never do anything with them since you add them dynamically. Add your dropdownlists where you create them (this should me when Page.IsPostBack == false) and keep that list in session. On postbacks, load your dropdowns from the list. You can compare them using the list you keep.