Possible to add to constructor from property aspects? #194

etkramer · 2022-07-28T19:00:45Z

etkramer
Jul 28, 2022

My goal is to give NotifyAttribute a parameter "dependsOn", which causes it to be notified any time some other property is changed - basically the reverse of AlsoNotify. To do this, my first instinct was to add something along the lines of

[Advice(Kind.After, Targets = Target.Constructor)]
public void AfterConstructor([Argument(Source.Instance)] object source, [Argument(Source.Name)] string propertyName, [Argument(Source.Triggers)] Attribute[] triggers)
{
    foreach (string dependencyProperty in triggers[0].DependsOn)
    {
        source.Subscribe(dependencyProperty, () => source.Raise(propertyName));
    }
}

However, this Advise doesn't actually seem to be triggered unless the aspect is applied directly to the class or the constructor - is there any way to have this be run used when the attribute is applied to a property instead?

pamidur · 2022-08-01T09:09:12Z

pamidur
Aug 1, 2022
Maintainer

Hi @BitCrusader ,thanks for your interest in the project. You have an interesting idea here.

Let's consider this class

class Test
{
  [Notify]
  public string Name {get; set;}

  [Notify (DependsOn = nameof(Name) )]
  public string FirstName {get; set;}
}

In this case [Notify (DependsOn = nameof(Name) )] will only be triggered if FirstName is changed, but will not be triggered if Name is changed. As per docs

When you apply

[Notify (DependsOn = nameof(Name) )]
class Test
{
  [Notify]
  public string Name {get; set;}

  [Notify (DependsOn = nameof(Name) )]
  public string FirstName {get; set;}
}

you effectively doing this:

class Test
{
  [Notify]
  [Notify (DependsOn = nameof(Name) )]
  public string Name {get; set;}

  [Notify (DependsOn = nameof(Name) )]
  [Notify (DependsOn = nameof(Name) )]
  public string FirstName {get; set;}
}

but it still won't trigger Aspect on FirstName if Name is changed. But you might see behaviour where :

  [Notify (DependsOn = nameof(Name) )]
  public string Name {get; set;}

To solve it you might need to keep track on the dependencies in the class, but figure this dependencies on the first hit. Like the following:

Advice is executed for Name
You get all attributes of all properties of the class via reflection and figure which ones have DependsOn. Find FirstName
Cache optionally
Raise events for dependent properties

0 replies

pamidur · 2022-08-01T09:13:19Z

pamidur
Aug 1, 2022
Maintainer

If it already the case. And you just need to apply aspects to all properties, you might just want to have different attributes. Like this:

[Notifiable]
class Test
{
  [Notify]
  public string Name {get; set;}

  [Notify (DependsOn = nameof(Name) )]
  public string FirstName {get; set;}

  public string FirstName {get; set;}
}

so like this Aspect will be executed for all props and then you can raise events only for those having [Notify]

0 replies

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etkramer Jul 28, 2022

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etkramer
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