# Using zip or enumerate within IF?
**URL:** https://discourse.julialang.org/t/using-zip-or-enumerate-within-if/132608
**Category:** New to Julia
**Created:** [September 23, 2025, 11:06pm UTC](https://discourse.julialang.org/t/using-zip-or-enumerate-within-if/132608 "2025-09-23T23:06:50Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Snowy](https://discourse.julialang.org/u/Snowy)
#### Post date: [September 23, 2025, 11:06pm UTC](https://discourse.julialang.org/t/using-zip-or-enumerate-within-if/132608/1 "2025-09-23T23:06:50Z")
Hello,
Is there a way to use zip() or enumerate() within the IF statement?
I’m looking for a safter way to run the code below. I’ve created structs to dispatch an appropriate model based off a “category” in a dataframe. Currently it’s only dispatching the custom models correctly because custom\_cats and custom\_cats\_structs are aligned (that is when looping through category: Custom 1, Struct: custom\_a is the appropriate choice).
It seems like doing something like zip(custom\_cats, custom\_cats\_structs) would be safer / more preferred way, but I can’t seem to figure out what the right syntax is.
Here’s what I have (which works, but again seems suboptimal):
```julia-auto
struct general end
struct custom_a end
struct custom_b end
df = DataFrame(category=["Normal 1", "Normal 2", "Normal 3", "Custom 1", "Custom 2"], X=[5, 4, 8, 9,10], Y =[1000,5000,3000,1200,5000])
cats = ["Normal 1", "Normal 2", "Normal 3", "Custom 1", "Custom 2"]
normal_cats = ["Normal 1", "Normal 2", "Normal 3"]
custom_cats = ["Custom 1", "Custom 2"]
custom_cats_structs = [custom_a(),custom_b()]
function mymodel(x::general)
println("Genearl Model Hello")
end
function mymodel(x::custom_a)
println("This is my first custom model")
end
function mymodel(x::custom_b)
println("This is my second custom model")
end
function run_models(cats,norm,cust,cust_structs)
for c in cats
println("working on $c")
if c in norm
mymodel(general())
elseif c in cust
n = 1
mymodel(cust_structs[n])
n+1
end
end
end
run_models(cats,normal_cats,custom_cats,custom_cats_structs)
```
Hope this makes sense. Thanks for your help.
---
### Author:  [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)
#### Post date: [September 23, 2025, 11:35pm UTC](https://discourse.julialang.org/t/using-zip-or-enumerate-within-if/132608/2 "2025-09-23T23:35:21Z")
```julia-auto
julia> a = [1, 2, 3, 4]; b = [100, 200, 300, 400];
julia> for (ai, bi) in zip(a, b)
println("ai: ", ai)
println("bi: ", bi)
end
ai: 1
bi: 100
ai: 2
bi: 200
ai: 3
bi: 300
ai: 4
bi: 400
```
---
### Author:  [@NonDairyNeutrino](https://discourse.julialang.org/u/NonDairyNeutrino)
#### Post date: [September 24, 2025, 4:35am UTC](https://discourse.julialang.org/t/using-zip-or-enumerate-within-if/132608/3 "2025-09-24T04:35:20Z")
Can we ask what the higher level goal is? Like, what end result do you want to get e.g. print something for each item in the data frame? While attempting a solution is good, it can lead to so-called [“XY problems”](https://xyproblem.info/). I also don’t quite understand what the current goal is either.
---
### Author:  [@danielwe](https://discourse.julialang.org/u/danielwe)
#### Post date: [September 24, 2025, 6:10am UTC](https://discourse.julialang.org/t/using-zip-or-enumerate-within-if/132608/4 "2025-09-24T06:10:05Z")
You essentially have an associative map. The datastructure for this is `Dict`. Here’s how I would do it:
```julia
struct General end
struct CustomA end
struct CustomB end
categories = ["Normal 1", "Normal 2", "Normal 3", "Custom 1", "Custom 2"]
custom_category_selectors = Dict("Custom 1" => CustomA(), "Custom 2" => CustomB())
function mymodel(x::General)
println("General Model Hello")
end
function mymodel(x::CustomA)
println("This is my first custom model")
end
function mymodel(x::CustomB)
println("This is my second custom model")
end
function run_models(categories, custom_selectors)
for c in categories
println("working on $c")
selector = get(custom_selectors, c, General()) # Defaults to General() when c is not a key in custom_selectors
mymodel(selector)
end
end
run_models(categories, custom_category_selectors)
```
```julia-auto
# Output
working on Normal 1
General Model Hello
working on Normal 2
General Model Hello
working on Normal 3
General Model Hello
working on Custom 1
This is my first custom model
working on Custom 2
This is my second custom model
```
---
### Author:  [@Snowy](https://discourse.julialang.org/u/Snowy)
#### Post date: [February 25, 2026, 4:27pm UTC](https://discourse.julialang.org/t/using-zip-or-enumerate-within-if/132608/5 "2026-02-25T16:27:03Z")
I’m trying to extend this to parent categories and could use some help.
From the previous solution, imagine that each category exists in a parent category. Simply, I could extend mymodel to include a parent category argument, but custom categories for each parent cat will differ slightly and I’m trying not to repeat myself for functions that aren’t any different. (But perhaps this is the best way?)
Doing something like the following, but I can’t figure out how to select the appropriate parent category and default
Here’s what I have thus far:
```julia
struct default_pc end
struct custom_pc1 end
struct custom_pc2 end
struct general_model end
struct custom_model1 end
struct custom_model2 end
categories = ["Normal 1", "Normal 2", "Normal 3", "Custom 1", "Custom 2"]
supercategories = ["custom_pc1","custom_pc2"]
supercats_mapping = Dict(
custom_pc1() => ["Custom 1" => custom_model1(), "Custom 2" => custom_model2()],
custom_pc2() => ["Custom 1" => custom_model1()]
)
function mymodel(pc::default_pc,m::general_model) println("This is the most generic model and will be used for any super category if a custom model isn't specified") end
function mymodel(pc::default_pc,m::custom_model1) println("this is the default custom model 1 and is used if the custom1 model isn't specified for a pc") end
function mymodel(pc::default_pc,m::custom_model2) println("this is the default custom model 2 and is used if the custom1 model isn't specified for a pc") end
function mymodel(pc::custom_pc1,m::custom_model1) println("this is the highly specific custom model 1 only used for pc1") end
function mymodel(pc::custom_pc1,m::custom_model2) println("this is the highly specific custom model 2 only used for pc1") end
function mymodel(pc::custom_pc2,m::custom_model1) println("this is the highly specific custom model 1 used only for pc2") end
function run_models(supercats,cats,mapping)
for s in supercats
println("working on $s")
for c in cats
println("working on $c")
pc_selector = get(mapping,s,default_pc())
println("pc selected: $pc_selector")
m_selector = get(mapping,c,general_model())
println("model selected: $m_selector")
mymodel(pc_selector,m_selector)
end
end
end
run_models(supercategories,categories,supercats_mapping)
```
However, I can’t figure out the right selection method here.
Ideally for custom\_pc1, it should run:
```julia
mymodel(pc::default_pc,m::general_model)
```
for Normal 1, 2, &3, then it should run:
```julia
mymodel(pc::custom_pc1,m::custom_model1) println("this is the highly specific custom model 1 only used for pc1") end
mymodel(pc::custom_pc1,m::custom_model2)
```
for custom 1 and custom 2.
For custom\_pc2, it should run:
```julia
mymodel(pc::default_pc,m::general_model)
```
for Normal 1, 2, 3
```julia
mymodel(pc::custom_pc2,m::custom_model1)
```
for Custom 1
and default back to:
```julia
mymodel(pc::default_pc,m::custom_model2)
```
for Custom 2 (since there is no custom 2 model specified for pc2)
So , I’m a bit lost on an elegant solution here. Perhaps I’ve been working on this problem too long.