Pagination

Pagination

List endpoints return one page at a time. OJS defaults to 20 items per page and allows at most 100. The library offers three ways to read them.

1. One page: ListAsync

ListAsync returns a PagedResult(Of T). ItemsMax is the total number of matches; Items holds the current page. Set Count and Offset on the query to choose the page.

Dim page = Await ojs.Submissions.ListAsync(New SubmissionQuery With {.Count = 50, .Offset = 100})
Console.WriteLine($"Showing {page.Items.Count} of {page.ItemsMax}")

var page = await ojs.Submissions.ListAsync(new SubmissionQuery { Count = 50, Offset = 100 });
Console.WriteLine($"Showing {page.Items.Count} of {page.ItemsMax}");

let! page = ojs.Submissions.ListAsync(SubmissionQuery(Count = 50, Offset = 100))
printfn "Showing %d of %d" page.Items.Count page.ItemsMax

2. Everything: ListAllAsync

ListAllAsync requests page after page and returns one list. Count on the query sets the page size, which defaults to 100. maxItems stops early.

Dim published = Await ojs.Submissions.ListAllAsync(
    New SubmissionQuery With {.Status = {SubmissionStatus.Published}}, maxItems:=1000)

var published = await ojs.Submissions.ListAllAsync(
    new SubmissionQuery { Status = new[] { SubmissionStatus.Published } }, maxItems: 1000);

let! published =
    ojs.Submissions.ListAllAsync(SubmissionQuery(Status = [| SubmissionStatus.Published |]), maxItems = 1000)

3. Streaming: Enumerate

Enumerate returns an IAsyncEnumerable(Of T) that fetches the next page only when you get to it. Use it to process large lists without holding them all in memory, or to stop early.

await foreach (var issue in ojs.Issues.Enumerate(new IssueQuery { IsPublished = true }))
{
    Console.WriteLine(issue.Identification);
    if (issue.Year < 2020) break;   // later pages are never requested
}

VB has no Await For Each. Use the enumerator directly:

Dim e = ojs.Issues.Enumerate(New IssueQuery With {.IsPublished = True}).GetAsyncEnumerator()
Try
    While Await e.MoveNextAsync()
        Console.WriteLine(e.Current.Identification)
    End While
Finally
    e.DisposeAsync().AsTask().GetAwaiter().GetResult()
End Try

In F#, use the FSharp.Control.TaskSeq package, or ListAllAsync:

open FSharp.Control
let issues = ojs.Issues.Enumerate(IssueQuery(IsPublished = true))
do! issues |> TaskSeq.iter (fun i -> printfn "%s" i.Identification)

Endpoints without paging

Some endpoints return everything at once as a List(Of T):

• contributors;
• publications of a submission;
• submission files;
• decisions;
• mailables;
• vocabularies;
• the email log.

Your own endpoints

Pager.GetAllAsync and Pager.Enumerate work with any function that fetches a page by offset:

Dim all = Await Paging.Pager.GetAllAsync(Of Issue)(
    Function(offset, ct) ojs.Issues.ListAsync(New IssueQuery With {.Offset = offset, .Count = 100}, ct))