Scenario: You have one pattern you want to match. You do not want to raise
a NoMatchError when the value fails to match this pattern.
Probably the best available thing to do is to use a `case` statement:
case foo do
%{bar: "baz"} -> "hello i match"
_ -> nil
end
However, that default case can get pretty repetitive when it's frequently
nothing, and it gets even more awkward inside of EEx:
<%= case foo do %>
<% %{bar: "baz"} -> %>
hello i match
<% _ -> %>
<% end %>
There's also `Kernel.match?/2`, which is awkward to use in an `if`
statement because it doesn't read like any pattern matching expression that
an Elixir developer has typically ever written:
if match?(%{bar: "baz"}, foo) do
"yes"
end
Here is an alternative idea, which I think is significantly easier to read
than the above options:
if_match %{bar: "baz"} = foo do
"yes"
else
"no"
end
if_match %{bar: "not baz"} = foo do
"yes"
end
<%= if_match %{bar: "baz"} = foo do %>
hello i match
<% end %>
Proof of concept code:
defmacro if_match(expression, do: do_clause) do
quote do
match(unquote(expression), do: unquote(do_clause), else: nil)
end
end
defmacro if_match({:=, _, [pattern, value]}, do: do_clause, else:
else_clause) do
quote do
case unquote(value) do
unquote(pattern) ->
unquote(do_clause)
_ ->
unquote(else_clause)
end
end
end
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