Learning How to Code and a build an App from scratch

[Hockeyman9474]

I am in desperate need of learning Coding and building a simple app from a blank template. I am experienced in some languages but I can't seem to get code to work within power apps. I find the information provied on the power apps site to be very basic and not very helpful. Can anyone suggest where I can look to find training.

[v-monli-msft]

Hi @Hockeyman9474,

After some research, I only find the below MS article about PowerApps for developer:

https://powerapps.microsoft.com/en-us/tutorials/dev-enterprise-intro/

PowerApps mainly makes it possible for Business Users to start creating an App without writing a single line of source code. And I think that is why MS do not have so much documentation on coding in PowerApps. 

Sorry for any inconvience.

Regards,

Mona

[Meneghino]

Hi @Hockeyman9474

I sympathise with your predicament, it took me a little while to get my head round how the coding in PowerApps works (it is coding, no matter what Microsoft keep saying).  Once you get your head round it then everything will be very clear.  And building apps from scratch is then much easier than trying to adapt the templates or automatically produced apps.

The best thing I can suggest is to start with a blank app and experiment with a purpose.  Just add a few controls and change their properties.

Is there anything in particular that you are having difficulty with?

[Hockeyman9474]

actually right now my biggest obstacle is a dropdown box. I prepopulate it with information from my datasource, which is fine. Ideally, I'd like the default to be a messgae like "Select..." but having it blank is ok as well. The default setting doesn't allow me to do that. The on change is coded to navigate to another screen, but because it's on change, to select what's in the dropdown, I have to make another selection  go back, and then select the one I wanted. On selectiondoesn't really do the trick also because once the user clicks the dropdown box is naviagtes without allowing the user to make a selection.

Any suggestions?

[Meneghino]

Hi @Hockeyman9474, sounds like a godo place to start.

Dropdown boxes in PowerApps do not currently allow for a blank selection, in other words they will always show one item from the Items property.

The Deafult property of the dropdown simply tells the dropdown what to show when no selection has (yet) been made, i.e. the initial value.  If the Default property is set to a value that is found in the column that you choose as your display value for the dropdown, then and only then, it will show this as the selection when nothing has yet been selected.  But if this value is not found, then it will just show the first item.  This is why setting default to "Select..." will not do anything, unless "Select..." is one of the values of your column.  I hope this is clear, but please let me know if it is not.

I am not sure what your issue is with the OnChange property.  Presumably it will be triggered if the user has made a selection (or to be precise, changed the selection from the existing/default selection).  So I am not sure why you say this does not allow you to make a selection.

[Hockeyman9474]

Thank you for the explanation as it makes a ton of sense. Let me give you a speciific example of the chnage property issue I am having.

The user comes into a screen with a drop down box pre-populated with 1-6. The on change event will navigate the user to another screen. 1 is set as the default value. If the user wants to select 1, as of now, they need to select another number, Navigate to the next screen, click the back button I created to go back, and then select 1.

Also, when they go back to the previous screen, is it possible for the box default value to reset to 1. Because, technically, the screens open on top of each other, it's not closing and therefore retains the last selection that was made. 

[Meneghino]

OK, clear.  Let's take each point one at a time.

---

The user comes into a screen with a drop down box pre-populated with 1-6. The on change event will navigate the user to another screen. 1 is set as the default value. If the user wants to select 1, as of now, they need to select another number, Navigate to the next screen, click the back button I created to go back, and then select 1.

I agree that this is ugly: there are two solutions:

1. Remove the OnChange property (i.e. set it to false) and add a navigation arrow control next to the dropdown.  But you didn't need me to tell you that.
2. Keep the OnChange but add another item to your Items property, say the value "Choose..." and set also this text as the Default property (I know that "Choose..." is a text value, but your numbers can also be text values and then you use the Value function to use them elsewhere)

---

Also, when they go back to the previous screen, is it possible for the box default value to reset to 1. Because, technically, the screens open on top of each other, it's not closing and therefore retains the last selection that was made. 

---

I am not sure what you mean by "the screens open on top of each other", but yes the screens never open or close, they are all always alive.  The way to reset the dropdown is to use its Reset property.  One way to do it automatically is to:

1. Set the OnVisible property of your screen to
   

   UpdateContext({ResetMyControls: true}); UpdateContext({ResetMyControls: false})

2. Set the Reset property of your dropdown simply to
   

   ResetMyControls

Please let me know how you get on.

[Hockeyman9474]

makes sense and trying it now. One question, how do I add choose as an item if my item control on the left references my datasource. In otherwords, can I still refer to the data source while Harcoding Choose...in addition or are you suggesting to add Choose to the datasource itself?

[Meneghino]

If you want to add "Choose..." as an item then you have a few possible approaches:

1. Hardcode in the datasource.  Easy but very bad form since it makes your database 'dirty'
2. Use the union of two tables on the fly, using this:
   https://powerusers.microsoft.com/t5/PowerApps-Forum/Solved-union-operator-or-function-to-append-one-...

Obviously the best is 2, please let me know if you need more guidance on how to do it.  On top of that, by caching your source you can also make performance much quicker.

[Hockeyman9474]

OK, I'm going to add the arrow. 

All options to reset box to default didn't work. It accepted the code but upon returning to the screen, the last selection still shows in the box.