Fixed when using withParameter with the 'Expression<Func<TViewModel, …

[glennawatson]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
It's a bug fix for: #1164

What is the current behavior? (You can also link to an open issue here)
#1164

What is the new behavior (if this is a feature change)?

Does this PR introduce a breaking change?
Don't believe so, just uses the existing view model When Any Value overloads used by the vmProperty field. This allows the ViewModel to be null initially.

Please check if the PR fulfills these requirements

• The commit follows our guidelines: https://github.com/reactiveui/reactiveui#contribute
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Other information:

…TParam>> withParameter' overload when having initially a null ViewModel property

[ghuntley]

Thanks for the PR Glenn. @reactiveui/reviewers-core can you please review.

[kentcb]

@glennawatson can you provide an example of code that previously failed that will now work with this PR applied?

I'm a little unclear from reading the PR description. It makes it sound like it's merely fixing existing behavior, but in fact the PR adds a whole new BindCommand overload. My understanding is that you've added the overload to facilitate delayed evaluation of the VM. Is that correct? Regardless, can you please provide some sample before/after code.

[glennawatson]

Sorry been away of late. Will get you a example in the next day or so.

[kentcb]

@glennawatson ping

[glennawatson]

Hi,

Not going to be able to get back to you guys for at least a week. Been in the hospital for a bit.

The main issue was using the Expression<Func<>> form, it didn't take into account changing values

ex thisValue => thisValue.VM.Blah

If VM wasn't set initially it wouldn't trigger properly.

So I changed it to use the same mechanism you use in the other code to handle that case.

[glennawatson]

If you look internally also, I added a new private method but changed the public facing method to use the new private method to use the better approach of using the new method that uses the following:

var withParamExpression = Reflection.Rewrite(withParameter.Body);
var withParamFunc = Reflection.ViewModelWhenAnyValue(viewModel, view, withParamExpression);

[glennawatson]

Anyway I'm not going to be able to help change the code sample for the next week or so due to technical restrictions, but hope that explanation helps.

[kentcb]

Thanks @glennawatson! I wish you a swift recovery.

If I get a chance I'll take a look at getting this merged for the next release.

[dnfclas]

@glennawatson,
Thanks for your contribution.
To ensure that the project team has proper rights to use your work, please complete the Contribution License Agreement at https://cla2.dotnetfoundation.org.

It will cover your contributions to all .NET Foundation-managed open source projects.
Thanks,
.NET Foundation Pull Request Bot

[glennawatson]

I signed the CLA btw, hasn't been updated here though since I did it over a week ago.

[coveralls]

Changes Unknown when pulling bb03ef8 on glennawatson:rxui7-master into ** on reactiveui:develop**.

[glennawatson]

I updated with the latest develop to pass the tests.

[glennawatson]

Closing due to CLA bot issues.