if/unless
if/unless 的值就是其对应运算表达式的运算的结果
cond
条件语句，类似于switch 但明显比switch强大. 运算结果为true即可返回值。
next_answer =
cond do
rem(current, 3) == 0 and rem(current, 5) == 0 ->
"FizzBuzz"
rem(current, 3) == 0 ->
"Fizz"
rem(current, 5) == 0 ->
"Buzz"
true ->
current
end
但是cond这类语句是不常用的，实际使用中多是使用pattern matching
defmodule FizzBuzz do
def upto(n) when n > 0, do: 1..n |> Enum.map(&fizzbuzz/1)
defp fizzbuzz(n), do: _fizzword(n, rem(n, 3), rem(n, 5))
defp _fizzword(_n, 0, 0), do: "FizzBuzz"
defp _fizzword(_n, 0, _), do: "Fizz"
defp _fizzword(_n, _, 0), do: "Buzz"
defp _fizzword( n, _, _), do: n
end
case
case File.open("case.ex") do
{ :ok, file } ->
IO.puts "First line: #{IO.read(file, :line)}"
{ :error, reason } ->
IO.puts "Failed to open file: #{reason}"
end
defmodule Users do
dave = %{ name: "Dave", state: "TX", likes: "programming" }
case dave do
%{state: some_state} = person ->
IO.puts "#{person.name} lives in #{some_state}"
_ ->
IO.puts "No matches"
end
end
Raising Exceptions 异常处理
使用raise函数抛出异常
iex> raise "Giving up"
** (RuntimeError) Giving up
#抛出带着异常类型及message
iex> raise RuntimeError
#** (RuntimeError) runtime error
iex> raise RuntimeError, message: "override message"
#** (RuntimeError) override message
