Nested indentation in show

question

#1

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

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

This is a Bar with critical value 0.7

Then for a type Baz

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

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.


#2

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 for displaying a tree. It works, but I do dearly miss CL’s special variables.


#3

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)
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