Is there any way I can call an instance of a function repeatedly with the function retaining internally the last state of the GPIO pin

Internals & Design
,
8

Since handling these indices by hand for every call seems really unsafe to me, I’d suggest giving the approaches in the topic rdeits linked a try! Like a functor for each pin you want:

julia> struct Edgedetector
           pinnumber::Int
           state::Ref{Bool}
           Edgedetector(pin, initialstate = false) = new(pin, Ref(initialstate))
       end

julia> function (e::Edgedetector)()
           newstate = getgpio(e.pinnumber)
           if newstate
               if !e.state[] println("Pin $(e.pinnumber): Button pressed!") end
           else
               if e.state[] println("Pin $(e.pinnumber): Button released!") end
           end
           e.state[] = newstate
           return newstate
       end

julia> getgpio(_) = rand(Bool); # mocked up

julia> p1 = Edgedetector(1)
Edgedetector(1, Base.RefValue{Bool}(false))

julia> p1()
false

julia> p1()
Pin 1: Button pressed!
true

julia> p1()
Pin 1: Button released!
false

julia> p1()
Pin 1: Button pressed!
true

Or if you don’t feel like carrying around an object per pin:

julia> let pinstates = Dict{Int,Bool}()
           global detectedge
           function detectedge(pinnumber::Int)
               newstate = getgpio(pinnumber)
               if haskey(pinstates, pinnumber)
                   if newstate
                       if !pinstates[pinnumber] println("Pin $(pinnumber): Button pressed!") end
                   else
                       if pinstates[pinnumber] println("Pin $(pinnumber): Button released!") end
                   end
               end
               pinstates[pinnumber] = newstate
               return newstate
           end
       end
detectedge (generic function with 1 method)

julia> getgpio(_) = rand(Bool)

julia> detectedge(1)
true

julia> detectedge(1)
Pin 1: Button released!
false

julia> detectedge(1)
false

julia> detectedge(1)
false

julia> detectedge(1)
Pin 1: Button pressed!
true

julia> detectedge(2)
false

julia> detectedge(2)
Pin 2: Button pressed!
true
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