collections

问题 I'm plotting graphs with D3. At this moment I'm doing it by binding this way: <d3:ChartPlotter x:Name="plotter" ItemsSource="Charts" Margin="20"> And I Add/Remove items to Charts and the plotter updates automatically. Works very well. The problem is that I need to bind from several collections, but obviously I can't set ItemsSource twice. I've read something about CompositeCollections, but almost every article is based on a StaticResource, that is not my case. <d3:ChartPlotter x:Name="plotter

问题 I have a class: public class ClientModelData { public int clientID { get; set; } public IList<int> LocationIDs { get; set; } } When I call it: ClientModelData obj = new ClientModelData(); obj.LocationIDs.Add(1); It throws an exception: `((System.Collections.Generic.ICollection<int>)(client.LocationID))' is null` 回答1: LocationIDs is not initialized therefore it is giving you the error. public IList<int> LocationIDs { get; set; } You should create an instance in the constructor public

问题 I have some code where I try to use the HashSet.retainAll() function. In the example code below, the HashSet contains the interface IPerson , but the equals functions in object Person is never reached. I have even tried to expose the equals function in the interface and several other things. I feel I have tried everything. How can I make retainAll() use my implemented equal function? class Person implements IPerson { private String name; public Person(String name){ this.name = name; }

问题 I have some unused collections in the MongoDb database. I've to find out when the CRUD operations done against collections in the database. We have our own _id field instead of mongo's default object_id. We dont have any time filed in the collections to find out the modification time. is there any way to find out the modification time of collections in mongodb from meta data? Is there any data dictionay informations like in oracle to find out this? please give some idea/workarounds 回答1: To

问题 let h = dict [(1, 2), (3, 4)] Console.WriteLine(h.Count) for i in h do Console.WriteLine(i) gives me 1 [(1, 2), (3, 4)] Two questions. Firstly, why does iterating over a dict give me back a sequence which only has 1 item, the dict itself? There is probably some logic behind this that will also affect other things I end up trying to iterate over. What does this mean for all the other Seq members exposed by dict (Any(), All(), Aggregate(), etc.)? Secondly, is there a good way to iterate over

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 5 years ago . Referring to this question: How to subtract dates from each other In Groovy, I've got a script that spits out the 5 largest values from a text file collection. How can I know what the indices of those values are? 回答1: If you have a list of things ie: def list = [ 'c', 'a', 'b' ] One way of knowing

问题 I define a collection that is supposed to map two parts of a line in a tab-separated text file: def fileMatches = [:].withDefault{[]} new File('C:\\BRUCE\\ForensicAll.txt').eachLine { line -> def (source, matches) = line.split (/\t/)[0, 2] fileMatches[source] << (matches as int)} I end up with entries such as filename:[984, 984] and I want [filename : 984] . I don't understand how fileMatches[source] << (matches as int) works. How might I get the kind of collection I need? 回答1: I'm not quite

问题 I have multiple methods that use multiple Collection parameters. I wanted to make things more specific so I thought using Forwarding Decorator The first question that comes to mind is: Is it an overkill to use the Forwarding Decoartor, am I missing a something more simpler , I mean this is very simple thanks to Guava but still? If Forwarding Decorator is the right path then It seems fine so far, but one thing I am not sure of is how do I get the base collection(ImmutableSet in this case) back

问题 So I've been told that my data model for separating my cells into sections is bad. I have 3 separate collections in my Tableview cartItems, groupedItems, and brandTitle in the CartVC. and I've been told this: "You need to start over with a single collection representing nothing but sections data (where each piece of section data will hold the corresponding row data), so you can mutate the model without going insane" and "...recommended to avoid multiple Arrays for the datasource of a table

问题 I have following data structure: Collection books: { _id: "ajafsoaifj3341", title: "Hello World", poems: [ { id: "12fjenofnoi23", addedAt: "2018-03-12...." }, { id: "563jdfb34jfrr", addedAt: "2018-03-10...." }, { id: "78a1ewqeqweq", addedAt: "2018-03-08...." } ] } Collection poems: { _id: "563jdfb34jfrr", title: "How to Join", author: "Smith" addedAt: "2017-12-21..." } I need to join these two collections to get the title of the poem. Something like: { _id: "ajafsoaifj3341", title: "Hello