# Nested indentation in show
**URL:** https://discourse.julialang.org/t/nested-indentation-in-show/7191
**Category:** General Usage
**Tags:** question
**Created:** [November 20, 2017, 3:17pm UTC](https://discourse.julialang.org/t/nested-indentation-in-show/7191 "2017-11-20T15:17:58Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [November 20, 2017, 3:17pm UTC](https://discourse.julialang.org/t/nested-indentation-in-show/7191/1 "2017-11-20T15:17:58Z")
When writing some methods for `show` for types in a package, I was wondering if there is any mechanism (or package) for reusing `show` methods for fields but nesting the indentation.
Eg suppose a type prints as
```julia
This is a Foo with 3x2 elements.
[1.0 1.0 1.0; 1.0 1.0 1.0; 1.0 1.0 1.0]
```
and a type `Bar` prints as
```julia
This is a Bar with critical value 0.7
```
Then for a type `Baz`
```julia
struct Bar
foo::Foo
bar::Bar
end
```
is there an organized way to write a `show` method that
1. reuses `show` code for the fields,
2. indents the fields.
Eg
```julia
This is a Bar with fields
This is a Foo with 3x2 elements.
[1.0 1.0 1.0; 1.0 1.0 1.0; 1.0 1.0 1.0]
This is a Bar with critical value 0.7
```
Solutions I have thought of:
1. use something other than indentation, eg `•`,
2. pass around the current indentation as an optional 3rd argument of `show`, defaulting to `0`.
Neither of these is very clean.
---
### Author:  [@cstjean](https://discourse.julialang.org/u/cstjean)
#### Post date: [November 20, 2017, 3:30pm UTC](https://discourse.julialang.org/t/nested-indentation-in-show/7191/2 "2017-11-20T15:30:26Z")
> [@Tamas\_Papp](#):
>
> pass around the current indentation as an optional 3rd argument of show, defaulting to 0.
I’m not aware of a generic solution for indentation, but the official way to pass arguments to `show` is to use `IOContext`. Eg. `show(IOContext(indent=get(io, :indent, 0)+2), mime, child_object)`. See also [this example](https://github.com/cstjean/FProfile.jl/blob/3cbfdb2e0e99a113366bf1df1da5882d19e583de/src/FProfile.jl#L293-L311) for displaying a tree. It works, but I do dearly miss CL’s special variables.
---
### Author:  [@ssfrr](https://discourse.julialang.org/u/ssfrr)
#### Post date: [November 20, 2017, 3:32pm UTC](https://discourse.julialang.org/t/nested-indentation-in-show/7191/3 "2017-11-20T15:32:24Z")
When I’ve need to do this in the past I’ve added an `indent` field to
[`IOContext`]
([https://docs.julialang.org/en/stable/stdlib/io-network/#Base.IOContext](https://docs.julialang.org/en/stable/stdlib/io-network/#Base.IOContext))
that gets added to whenever we need to nest another level. It won’t work
with `Base` types or types from other packages, but within a package you
can use it for all your types that could be nested within each other.
-s
---
### Author:  [@putianyi888](https://discourse.julialang.org/u/putianyi888)
#### Post date: [April 4, 2024, 9:59am UTC](https://discourse.julialang.org/t/nested-indentation-in-show/7191/4 "2024-04-04T09:59:26Z")
updated link
[https://docs.julialang.org/en/v1/base/io-network/#Base.IOContext](https://docs.julialang.org/en/v1/base/io-network/#Base.IOContext)
---
### Author:  [@saulrh](https://discourse.julialang.org/u/saulrh)
#### Post date: [January 3, 2025, 7:34am UTC](https://discourse.julialang.org/t/nested-indentation-in-show/7191/5 "2025-01-03T07:34:39Z")
If you want a kludgey half-solution that works even for types you don’t own, you can have your types make and pass down an `IOBuffer` instead of the `io` arg when they recurse into `show` on their children, then re-emit each line of that buffer with indentation added to the front. It looks sort of like this:
```julia
function Base.show(io::IO, mime, x::Bar)
println(io, "This is a Bar with fields")
buffer = IOBuffer()
for c in x.children
show(buffer, mime, c)
for line in split(String(take!(buffer)), "\n")
println(io, " ", line)
end
end
end
```
Other types won’t be able to add new levels of indentation, so e.g. `Dict`s might be a touch ugly, but at least now even multiline children will be properly indented inside your own types.
(Yes, the performance is horrible, almost certainly outright quadratic in the depth unless `IOBuffer` and `String` and `take!` are all doing some _deep_ cooperative pointer-shuffling magic, but it’s pretty-printing for human inspection so N is like eight at most, lol. 😛 )
---
### Author:  [@frankier](https://discourse.julialang.org/u/frankier)
#### Post date: [June 17, 2025, 11:32am UTC](https://discourse.julialang.org/t/nested-indentation-in-show/7191/6 "2025-06-17T11:32:02Z")
I agree that that code might be the best pragmatic solution at the moment. There has been [GitHub - KristofferC/IOIndents.jl: Simple writing of indented and aligned text](https://github.com/KristofferC/IOIndents.jl) and [GitHub - tpapp/IndentWrappers.jl: Wrapper type for indentation management for plain text printing.](https://github.com/tpapp/IndentWrappers.jl) and [GitHub - tpapp/IndentWrappers.jl: Wrapper type for indentation management for plain text printing.](https://github.com/tpapp/IndentWrappers.jl) but both have been abandoned.