Gets a value and updates a nested data structure via the given path.

This is similar to get_and_update_in/3, except the path is extracted via a macro rather than passing a list. For example:

get_and_update_in(opts[:foo][:bar], &{&1, &1 + 1})

Is equivalent to:

get_and_update_in(opts, [:foo, :bar], &{&1, &1 + 1})

This also works with nested structs and the struct.path.to.value way to specify paths:

get_and_update_in(struct.foo.bar, &{&1, &1 + 1})

Note that in order for this macro to work, the complete path must always be visible by this macro. See the "Paths" section below.

Examples

iex> users = %{"john" => %{age: 27}, "meg" => %{age: 23}}
iex> get_and_update_in(users["john"].age, &{&1, &1 + 1})
{27, %{"john" => %{age: 28}, "meg" => %{age: 23}}}

Paths

A path may start with a variable, local or remote call, and must be followed by one or more:

• foo[bar] - accesses the key bar in foo; in case foo is nil, nil is returned

• foo.bar - accesses a map/struct field; in case the field is not present, an error is raised

Here are some valid paths:

users["john"][:age]
users["john"].age
User.all()["john"].age
all_users()["john"].age

Here are some invalid ones:

# Does a remote call after the initial value
users["john"].do_something(arg1, arg2)

# Does not access any key or field
users