Accessing variables in a ModelingToolkit system

Specific Domains Modelling & Simulations
2

You can use the very new @nonamespace

using ModelingToolkit
@parameters v, t
@named d = ODESystem(Equation[],t,[],[v])
@named c = ODESystem(Equation[],t,[],[v],systems=[d])
@named b = ODESystem(Equation[],t,[],[v],systems=[c])
@named a = ODESystem(Equation[],t,[],[v],systems=[b])

a.b.c.d.v # a₊b₊c₊d₊v

@nonamespace a.b.c.d.v # v
@nonamespace tmp = a.b.c.d # Model d with 0 equations
tmp.v # d₊v

@nonamespace tmp = a.b # Model b with 0 equations
tmp.c.d.v # b.c.d.v

or getproperty(…; namepsace=false)

@parameters V, W
@named sub = ODESystem(Equation[],t,[],[V,W])
@named od = ODESystem(Equation[],t,[],[V,W],systems=[sub])

substate(sys,sub,state) = getproperty(getproperty(sys,Symbol(sub),namespace=false), Symbol(state))
substate(od, "sub", "W") # sub₊W

@variables V[1:3], W[1:3]
@named sub = ODESystem(Equation[],t,[V...,W...],[])
@named od = ODESystem(Equation[],t,[V...,W...],[],systems=[sub])
substate(sys,sub,state,i) = getproperty(getproperty(sys,Symbol(sub),namespace=false), Symbol("$(state)$(join('₀'+d for d in reverse(digits(i))))"))
substate(od,"sub","W",1) # sub₊W₁
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