I'm struggling with something I'm sure I should be able to do quite quick with Linq-to-Obj
Have 27 flowers, need a collection of Flower[] containing 5 items split over, roughly 6 records;
List<Flowers[]> should contain 6 Flowers[] entities, and each Flowers[] array item should contain 5 flower objects.
I currently have something like:
List<Flowers[]> flowers;
int counter = 0;
List<Flowers>.ForEach(delegate (Flower item) {
if (counter <= 5){
// add flowers to array, add array to list
}
});
I'm trying to optimise this as it's bulky.
[Update]
I can probably to an array push on objects, removing the items I'v already run through, but is there not an easier way?
var ITEMS_IN_GROUP = 5;
var result = list.Select((Item, Index) => new { Item, Index })
.GroupBy(x => x.Index / ITEMS_IN_GROUP)
.Select(g => g.Select(x=>x.Item).ToArray())
.ToList();
You may also want to try morelinq's Batch
Related
First, I had this: parts = parts.filter(part => part.id !== change.doc.id);
So, data is an Array and it gets 'clobbered' with a new 'filtered' Array.
Vue didn't seem keen on detecting the change and updating my DOM.
So, I saw this. Specifically: To deal with caveat 2, you can use splice:
I refactored (or is it 'de-factored' b/c my code 'grew'?) to this:
// Get index of part removed
const index = parts.forEach((part, i) => {
if (part.id === change.doc.id) {
return i;
}
});
parts.splice(index, 1);
She works...but really? Do I have to do this way? 😬
parts.splice(parts.findIndex(part => part.id === change.doc.id), 1);
I got the splice in there while still keeping as 1 line, so m happy! 🤓
I am new to Umbraco. I have a list of items in a content named Videos. Each item have a specific category. I need to retrieve 'n' number of items from each category. Some one please help. Also am using MixItUp jquery plugin to display the items.
// this will bring up all items from the list
var items = Umbraco.TypedContent(Model.Content.Id).Children.Where(x => x.DocumentTypeAlias == "videoItem" && x.IsVisible());
// Here am trying to bring 5 items under category "Testimonial"
var allItems = items.Where(x => x.GetPropertyValue("category") == "Testimonial").Take(5);
But I didn't found any output. Please help.
Your second line of code should read:
var allItems = items
.Where(x => x.GetPropertyValue<string>("category") == "Testimonial")
.Take(5);
Rather than simply cast the result to string, this will try and convert the object to the desired type if it isn't already - see here.
If you're using the new ModelsBuilder (which is awesome) you also have the option of strongly typing the whole process.
var items = Model.Content.Children<VideoItem>().Where(x => x.IsVisible());
var allItems = items.Where(x => x.Category == "Testimonial").Take(5);
I'm currently trying to find out how to set items to be selected on a list in ST2.
I've found the following:
l.select(0, true);
l.select(1, true);
which would select the first 2 items on my list. But the data coming from the server is in csv format string with the ids of the items in the list to be selected.
e.g. "4, 10, 15"
So I currently have this code at the moment.
doSetSelectedValues = function(values, scope) {
var l = scope.getComponent("mylist");
var toSet = values.split(",");
// loop through items in list
// if item in list has 'id' property matching whatever is in the toSet array then select it.
}
The problem is I can't seem to find a way of iterating over the items in the list and then inspect the "id" property of the item to see if it matches with the item in the array.
l.getItems()
Doesn't seem to return an array of items. The list is populated via a store with the "id" & "itemdesc" properties. I just want to be able to select those items from a csv string. I've scoured the Api on this and I can't seem to find a way of iterating over the items in the list and being able to inspect its backing data.
the Ext.List's items are not the items you are looking for. The items under the Ext.List object are those:
Ext.create('Ext.List', {
fullscreen: true,
itemTpl: '{title}',
store: theStore,
**items: [item1, item2]**
});
Granted, usually an Ext.List doesn't have items like these. What you are looking for are the Ext.Store items. The Ext.Store items are the exact same items in the same order as presented in the Ext.List.
To iterate over those, and select the corresponding items in the list, do the following:
var s = l.getStore();
var itemIndicesToSelect = [];
for (var i = 0 ; i < s.data.items.length ; i++){
if (arrayContainsValue(toSet, s.data.items[i].data.id)){
itemIndicesToSelect.push(i);
}
}
for (var i = 0 ; i < itemIndicesToSelect.length ; i++){
l.selectRange(itemIndicesToSelect[i], itemIndicesToSelect[i], true);
}
You would have to implement the function arrayContainsValue (one possible solution).
doSetSelectedValues = function(values, scope) {
var l = scope.getComponent("mylist"),
store = l.getStore(),
toSet = values.split(",");
Ext.each(toSet, function(id){
l.select(store.getById(id), true);
});
}
I want to fetch Hierarchical/Tree data something like below from a Table which has following definiton.
Tree Table:
"""""""""""
Id |ParentId
"""""""""""
Work1|null
Work2|Work1
Work3|Work2
...
Required Query result Data (no need to be tabbed)- If I Pick 'Work1' I should complete Ids which are under its root something like below. If I pick 'Work2' then also I should complete Ids above and below its root.
> Work1
----------
> Work2
----------
> Work3
---------
What is the best way in NHibernate to fetch data in the above scenario in optimized manner.
To find out what the "best way" is, more information regarding the actual scenario would be needed. What kind of "optimization" are you looking for? Minimal amount of data (only the rows you are really going to need) or minimal number of SQL queries (preferably one roundtrip to the database) or any other?
Scenario 1: Menu or tree structure that is loaded once and kept in memory for longer periods of time (not a list that updates every few seconds). Small number of rows in the table (small is relative but I'd say anything below 200).
In this case I would just get the whole table with one query like this:
var items = session.Query<Work>()
.Fetch(c => c.ParentWork)
.Fetch(c => c.ChildWorks).ToList();
var item = session.Get<Work>(id);
This will result in a single SQL query which simply loads all the rows from the table. item will contain the complete tree (parents, grandparents, children, etc.).
Scenario 2: Large number of rows and only a fraction of rows needed. Only few levels in the hierarchy are to be expected.
In this case, just load the item and let NHibernate to the rest with lazy loading or force it to load everything by writing a recursive method to traverse parents and children. This will cause a N+1 select, which may or may not be slower than scenario 1 (depending on your data).
Here is a quick hack demonstrating this:
var item = session.Get<Work>(id);
Work parent = item.ParentWork;
Work root = item;
// find the root item
while (parent != null)
{
root = parent;
parent = parent.ParentWork;
}
// scan the whole tree
this.ScanChildren(root);
// -----
private void ScanChildren(Work item)
{
if (item == null)
{
return;
}
foreach (Work child in item.ChildWorks)
{
string name = child.Name;
this.ScanChildren(child);
}
}
Edit:
Scenario 3: Huge amount of data. Minimal number of queries and minimal amount of data.
In this case, I would think not of a tree structure but of having layers of data that we load one after another.
var work = repo.Session.Get<Work>(id);
// get root of that Work
Work parent = work.ParentWork;
Work root = work;
while (parent != null)
{
root = parent;
parent = parent.ParentWork;
}
// Get all the Works for each level
IList<Work> worksAll = new List<Work>() { root };
IList<Work> worksPerLevel = new List<Work>() { root };
// get each level until we don't have any more Works in the next level
int count = worksPerLevel.Count;
while (count > 0)
{
worksPerLevel = this.GetChildren(session, worksPerLevel);
// add the Works to our list of all Works
worksPerLevel.ForEach(c => worksAll.Add(c));
count = worksPerLevel.Count;
}
// here you can get the names of the Works or whatever
foreach (Work c in worksAll)
{
string s = c.Name;
}
// this methods gets the Works in the next level and returns them
private IList<Work> GetChildren(ISession session, IList<Work> worksPerLevel)
{
IList<Work> result = new List<Work>();
// get the IDs for the works in this level
IList<int> ids = worksPerLevel.Select(c => c.Id).ToList();
// use a WHERE IN clause do get the Works
// with the ParentId of Works in the current level
result = session.QueryOver<Work>()
.Where(
NHibernate.Criterion.Restrictions.InG<int>(
NHibernate.Criterion.Projections.Property<Work>(
c => c.ParentWork.Id),
ids)
)
.Fetch(c => c.ChildWorks).Eager // this will prevent the N+1 problem
.List();
return result;
}
This solution will not cause a N+1 problem, because we use an eager load for the children, so NHibernate will know the state of the child lists and not hit the DB again. You will only get x+y selects, where x is the number of selects to find the root Work and y is the number of levels (max depth of he tree).
Is there a lambda equivalent of IN? I will like to select all the funds with ids either 4, 5 or 6. One way of writing it is:
List fundHistoricalPrices = lionContext.FundHistoricalPrices.Where(fhp => fhp.Fund.FundId == 5 || fhp.Fund.FundId == 6 || fhp.Fund.FundId == 7).ToList();
However, that quickly becomes unmanageable if I need it to match say 100 different fundIds. Can I do something like:
List
fundHistoricalPrices =
lionContext.FundHistoricalPrices.Where(fhp
=> fhp.Fund.FundId in(5,6,7)).ToList();
It's somewhere along these lines, but I can't quite agree with the approach you have taken. But this will do if you really want to do this:
.Where(fhp => new List<int>{5,6,7}.Contains( fhp.Fund.FundId )).ToList();
You may want to construct the List of ids before your LINQ query...
You can use the Contains() method on a collection to get the equivalent to in.
var fundIds = new [] { 5, 6, 7 };
var fundHistoricalPrices = lionContext.FundHistoricalPrices.Where(fhp => fundIds.Contains(fhp.Fund.FundId)).ToList();
You could write an extension method like this :
public static bool In<T>(this T source, params T[] list)
{
if(null==source) throw new ArgumentNullException("source");
return list.Contains(source);
}
Then :
List fundHistoricalPrices = lionContext.FundHistoricalPrices.Where(fhp => fhp.Fund.FundId.In(5,6,7)).ToList();
No, the only similar operator i'm aware of is the Contains() function.
ANother was is to construct your query dynamically by using the predicate builder out of the LINQkit: http://www.albahari.com/nutshell/predicatebuilder.aspx
Example
int[] fundIds = new int[] { 5,6,7};
var predicate = PredicateBuilder.False<FundHistoricalPrice>();
foreach (int id in fundIds)
{
int tmp = id;
predicate = predicate.Or (fhp => fhp.Fund.FundId == tmp);
}
var query = lionContext.FundHistoricalPrices.Where (predicate);