# MTK - instantiate \*vectors\* of models?
**URL:** https://discourse.julialang.org/t/mtk-instantiate-vectors-of-models/113487
**Category:** Modelling & Simulations
**Created:** [April 25, 2024, 7:58am UTC](https://discourse.julialang.org/t/mtk-instantiate-vectors-of-models/113487 "2024-04-25T07:58:46Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@BLI](https://discourse.julialang.org/u/BLI)
#### Post date: [April 25, 2024, 7:58am UTC](https://discourse.julialang.org/t/mtk-instantiate-vectors-of-models/113487/1 "2024-04-25T07:58:46Z")
Is it possible to instantiate _vectors_ of models in MTK?
What I mean is the following. I have created a re-usable “class” which I have named `Well`. In the past, I have instantiated several copies of this model and used the instances in equations, example:
```julia
@mtkmodel Field begin
# Components used
@components begin
...
w1 = Well()
w2 = Well()
...
end
# Equations for connecting components
@equations begin
w1.p_i ~ ...
w2.p_i ~ ...
...
x ~ w1.p_i + w2.p_i + ...
end
end
```
This works. However, with many instances of `Well`, the code is ugly.
What I would like to do is something similar to:
```julia
@mtkmodel Field begin
# Components used
@components begin
...
w[1:5] = Well()
...
end
# Equations for connecting components
@equations begin
w[1:5].p_i .~ ...
...
x ~ sum(w[1:5].p_i)
end
end
```
When I do this, and try to build the model:
```julia
@mtkbuild f = Field()
```
I get an error message:
```julia
type Array has no field p_i
```
**Question** :
1. Is it _possible_ to use arrays to instantiate models?
2. If yes, how do I need to modify my code?
---
### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [June 15, 2024, 10:34am UTC](https://discourse.julialang.org/t/mtk-instantiate-vectors-of-models/113487/2 "2024-06-15T10:34:15Z")
This is documented in the `@mtkmodel` macro page:
[Components and Connectors · ModelingToolkit.jl](https://docs.sciml.ai/ModelingToolkit/stable/basics/MTKModel_Connector/#What-can-an-MTK-Model-definition-have)?
```julia
@components begin
model_a = ModelA(; k_array)
model_array_a = [ModelA(; k = i) for i in 1:N]
model_array_b = for i in 1:N
k = i^2
ModelA(; k)
end
end
```