help! something I don't understand

[111182]

when I learning something about blueprints, there is one node teacher told me programming like this:

In this part, the only thing the function “Initialize Speaker Logic” can do is setting the value of an array:

but, if a program like this:

then, something when wrong. I don’t what happened and what the difference between these. So I think I need some help. TKX!

[ClockworkOcean]

Is the speaker list array variable local to the function?

[111182]

Nope, it’s just a variable. It seems that I can’t create a new variable and initialize it at the same time, or I need to turn it into a local variable?

[Pantoth]

Hm as far as I know there should be no difference?

I’ve tried it within a new project with some Actors and the Level Blueprint and it works without Promoting it to a variable. The function prints out a Print String for every BP_TestActor that was found.

What exactly isn’t working on your side?

[111182]

"Blueprint runtime error: “Accessed None trying to read property Speaker_Logic_Reference”
Actually it’s a sample product provided by epic online learning platform. When I click an struct, it calls this:

and the function “Set Cabinet Material” references variable “Speaker List”.
it seems that the bp doesn’t create an variable to be called but i don’t know why did this happen

[Pantoth]

Not completely sure how your BP setup looks like, sorry

Try to use some very basic debugging method: The Print String node. Print out some of the values you’re trying to get / set. For example the Array of Speaker BP’s or the (for me at least) very strange Cabinet Index. So you can pinpoint, when or where exactly your Blueprint fails.

[111182]

Got it, thank u so much