# Schedule agents by type

**URL:** <https://discourse.julialang.org/t/schedule-agents-by-type/75858>\
**Category:** Specific Domains\
**Tags:** agents\
**Created:** [February 5, 2022, 1:26pm UTC](https://discourse.julialang.org/t/schedule-agents-by-type/75858 "2022-02-05T13:26:40Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![imantha](https://avatars.discourse-cdn.com/v4/letter/i/6a8cbe/32.png) [@imantha](https://discourse.julialang.org/u/imantha)\
**Post date:** [February 5, 2022, 1:26pm UTC](https://discourse.julialang.org/t/schedule-agents-by-type/75858/1 "2022-02-05T13:26:41Z")

</div>

Hi, I am wondering whether there is a way to get a list of agents by their type?

For example if there are two types of agents

```julia
mutable struct Casualty <: AbstractAgent
      ...
end

mutable struct Rescuer <: Abstract Agent
    ...
end

```

I am able to get keyset of all agents in a model provided `Schedulers.fastest` is used through the following syntax, `ids = model.scheduler(model)`. However if I were to use `Schedulers.by_type` instead, I am wondering how would I go about getting a keyset pertaining to one type of agent (note for the latter `model.scheduler(model)` ends up with a Method error.

```julia
function main2()
    model = AgentBasedModel(
        Union{Casualty, Rescuer},
        OpenStreetMapSpace(OSM.TEST_MAP),
        scheduler = Schedulers.by_type,
    )

    for id = 1:5
        pos = random_position(model)
        init_pos = (775, 775, 0.0)
        casualty = Casualty(id, pos, rand([1,2,3]), true, false,false, false, false, false, false)
        rescuer = rescuer = Rescuer(id + 5, init_pos, "inactive", (0, 0, 0.) ,Array{Casualty}([]))
        add_agent_pos!(casualty, model)
        add_agent_pos!(rescuer, model)
    end
    return model
end

#get a keyset of a specific agent ?

ids = model.scheduler(model)
ERROR: MethodError: no method matching by_type(::AgentBasedModel{Agents.OSM.OpenStreetMapSpace, Union{Casualty, Rescuer}, typeof(Agents.Schedulers.by_type), Nothing, Random.TaskLocalRNG})

```

---

<div class="post-metadata">

**Author:** ![fbanning](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/fbanning/32/14972_2.png) [@fbanning](https://discourse.julialang.org/u/fbanning)\
**Post date:** [February 5, 2022, 3:26pm UTC](https://discourse.julialang.org/t/schedule-agents-by-type/75858/2 "2022-02-05T15:26:00Z")

</div>

`Schedulers.by_type` works differently than how you use it here. See [here](https://juliadynamics.github.io/Agents.jl/stable/api/#Agents.Schedulers.by_type). It’s for activating agents in certain order determined by their type.

To do what you want to do, you need to construct an iterable (e.g. a vector) of all the agent ids for agents of a given type. Something like

```julia
function by_type(T, model)
    ids = Int[]
    for id in allids(model)
        if model[id] isa T 
            push!(ids, id)
        end
    end
    return ids
end

```

should work, I suppose? I don’t have a mixed agent model at hand right now, so I can’t test it. Worked just fine for a model with a single agent type.