Downloading multiple files (coroutine, yield)

Hello there! I'm new to Unity (picked it up a couple of days ago). I've programmed a lot in the past, so I've come on quite quickly, and c# is actually pretty nice!

I've got a database of content with metadata (thumbs, title, etc) aand written a ghetto api to provide those via the web. I want to cache all the metadata, and pulldown the main files on the fly as the user selects them. I can call the APIs fine, but I'm wondering how I download stuff in serial. I don't fully grasp how coroutine and yield interact, and I'm loathe to set up blocking stuff before I understand more.

Here's the pseudocode:

GetIDsFromServer() (returns array of IDs)
IterateThroughIDsAndCheckStatus
- (returns int 0, 1, 2 - 0 is failed, 1 is locally cached, 2 is remotely requested).
- if it's cached, wahoo, skip
- if it's remote, pull down the data
RenderThumbnailsInNiceScrollableList()

I've got all the bits and pieces working in isolation but I'm now wondering exactly how I request the metadata in serial. Essentially, I want to a status bar with something like "Contacting Server.." then "Found 7 new Scenes.." then "Downloading 1/7", 2/7, etc.

I discovered nested coroutines which seems to solve my problem, but I don't understand how to make IterateThroughIDsAndCheckStatus return an int. It seems if I want to nest coroutines, IterateThroughIDsAndCheckStatus needs to be an IENumerator and therefore can't return an int? Or did I miss something entirely obvious?

 

Check out this post, a few good options here for getting data out of a coroutine:
http://answers.unity3d.com/questions/24640/how-do-i-return-a-value-from-a-coroutine.html

 

thank you

goldenslot บนมือถือ

 

Thank you very much. In the end, I just set up some conditions in Update() (downloadActive, numberOfDownloads) that tracked the status and started the next download, displaying progress to the user. It's a dirty kludge, but it works.

 

Thank you very much. Very valuable information!

 

I made something that can download any amount of files, display progress, and you can use simple callbacks or a Mono component.

Its very simple!

https://github.com/jpgordon00/UnityGroupDownloader

 

Error :

IndexOutOfRangeException: Index was outside the bounds of the array.
UFD.UnityFileDownloader._Dispatch () (at Assets/UnityFileDownloader-main/UnityFileDownloader.cs:258)
UFD.UnityFileDownloader.Download () (at Assets/UnityFileDownloader-main/UnityFileDownloader.cs:200)
NewBehaviourScript.Download () (at Assets/NewBehaviourScript.cs:37)
System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__7_0 (System.Object state) (at <c9d3ffd4b98649ee9989e1908eaca019>:0)
UnityEngine.UnitySynchronizationContext+WorkRequest.Invoke () (at <c399efc08928422d8828d74a2b19ffba>:0)
UnityEngine.UnitySynchronizationContext.Exec () (at <c399efc08928422d8828d74a2b19ffba>:0)
UnityEngine.UnitySynchronizationContext.ExecuteTasks () (at <c399efc08928422d8828d74a2b19ffba>:0)



Hi i tried to use your code and used sample code to download but i am getting this error. Kindly Support

 

This error requires no support and requires no forum posting.

You are the only person who can fix this error, and it is ALWAYS the same steps. ALWAYS.

How to fix a NullReferenceException error

https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

Three steps to success:
- Identify what is null <-- any other action taken before this step is WASTED TIME
- Identify why it is null
- Fix that

 

And i have to give credentials to get access to the files. How to do?

 

I actually fixed the issue @samtcs. It was an error relating to code that I released under my GitHub - so thanks for helping me improve it!