Dynamic unit conversions

[tmilnthorp]

• UnitConverter: Change from hard coded switch statement to lookup of conversion functions
• Allow consumers to add their own conversion functions between their own quantity types

Idea for #478. I'll add more commentary there.

[tmilnthorp]

This isn't completely fleshed out yet. Just to show an idea, so don't merge it yet.

Comments in #478

[angularsen]

Interesting approach, it definitely unlocks the ability to add explicit unit-to-unit conversions even across quantities. I'll comment further in the issue #478 instead.

[angularsen]

New changes looks good, but still need to digest how and why this will be used. Continuing discussion in issue.

[angularsen]

Adding a summary from prior discussion here:

As for direct conversions, I think that sounds like a good idea regardless:

1. A single piece of code to handle all conversions, generically
2. Route existing unit-base and base-unit conversions through it
3. Ability to add higher-precision direct conversions
4. Ability to add cross-quantity conversions
5. Ability to plug in 3rd party conversions of 3rd party unit enums
6. Compatible with the new dynamic Quantity in Improve working dynamically with units and quantities #576 for converting dynamically

[angularsen]

Re-reading this now.

[angularsen]

I think this is looking pretty good. I just took the liberty of adding some changes directly to the branch, please review them and see what you think.

https://github.com/angularsen/UnitsNet/pull/588/commits

[angularsen]

When this is merged, this wiki should be updated on the new capability to add unit conversions:
https://github.com/angularsen/UnitsNet/wiki/Extending-with-Custom-Units

[tmilnthorp]

More work to do here (including doc obviously after warnings-as-errors). Just merging to keep up to date.

[angularsen]

@tmilnthorp I took this for spin locally and added some improvements. I think this is ready to merge now, but waiting for you to check out the latest changes.

I was specifically interested in seeing how we can improve support for third party quantities and units and added some test cases for that. It works pretty well by now, you can parse units, parse quantities and convert between quantities using only custom types. We still enforce the requirement of implementing IQuantity, which I did find awkward when adding an example HowMuch quantity since that interface is pretty bloated and most of it is not used for simple conversions and parsing.

I think there is definitely an opportunity to support simple POCO classes and structs without them having to implement IQuantity, but I didn't want to clutter this PR with that.

If you have time, I'd also love to merge #656 .

[angularsen]

Looks good to me, waiting for you to review my latest improvements.

[angularsen]

This needs to port the powershell changes to the new C# codegen scripts.

Update: Fixed.

[angularsen]

@tmilnthorp I think this one is good to go. Two months ago I made some changes to it and I'd like you to look over them whenever you find the time so we can get this puppy merged :)

[tmilnthorp]

Looks good to me!

[angularsen]

Sweet!

[angularsen]

Release UnitsNet/4.30.0 · angularsen/UnitsNet