shahryarjb
How to edit and sort index of nested map in a list
Hello, I have a list like this:
[
%{
index: 1,
params: %{
id: "test1",
title: "test of one",
width: "col-sm-12"
},
type: "Heading"
},
%{
index: 3,
params: %{
id: "test3",
title: "test of one",
width: "col-sm-12"
},
type: "Heading"
},
%{
index: 5,
params: %{
id: "test5",
title: "test of one",
width: "col-sm-12"
},
type: "Heading"
},
]
and I want to change all index number and sort them but with new index which starts 0 like this
[
%{
index: 0,
params: %{
id: "test1",
title: "test of one",
width: "col-sm-12"
},
type: "Heading"
},
%{
index: 1,
params: %{
id: "test4",
title: "test of one",
width: "col-sm-12"
},
type: "Heading"
},
%{
index: 2,
params: %{
id: "test5",
title: "test of one",
width: "col-sm-12"
},
type: "Heading"
},
]
I need this because maybe a map is deleted in a list and the map deleted index will be null and I want to re-index all the map after every deleting
Thanks
Most Liked
chasers
If you wanted to use with_index you could do this but you’d be going through those more than you need to:
Enum.with_index(list) |> Enum.map(fn {x, index} -> Map.put(x, :index, index) end)
eksperimental
Here’s a one-liner.
Enum.reduce(list, {0, []}, fn element, {index, list_acc} -> {index + 1, [%{element | index: index} | list_acc]} end)
|> elem(1)
|> Enum.reverse()
benwilson512
Hi @shahryarjb, what have you tried so far?
shahryarjb
I think this should be this 
new_blocks
|> Enum.with_index
|> Enum.map(fn {x, index} ->
Map.merge(x, %{index: index})
end)
|> IO.inspect()
chasers
Like this?
defmodule MyApp.Indexer do
def put_index(list, index \\ 0)
def put_index([], _) do
[]
end
def put_index([head | tail], index) do
[Map.put(head, :index, index) | put_index(tail, index + 1)]
end
end
Check out the Enum.with_index source: https://github.com/elixir-lang/elixir/blob/v1.11.2/lib/elixir/lib/enum.ex#L3152
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