Kaur v1.1.0 Kaur.Result View Source

Utilities for working with “result tuples”.

  • {:ok, value}
  • {:error, reason}

Link to this section Summary

Functions

Calls the next function only if it receives an ok tuple. Otherwise it skips the call and returns the error tuple

Calls the first function if it receives an error tuple, and the second one if it receives an ok tuple

Creates a new error result tuple

Checks if a result_tuple is an error

Promotes any value to a result tuple. It excludes nil for the ok tuples

Converts an Ok value to an Error value if the predicate is not valid

Calls the next function only if it receives an ok tuple. The function unwraps the value from the tuple, calls the next function and wraps it back into an ok tuple

Calls the next function only if it receives an error tuple. The function unwraps the value from the tuple, calls the next function and wraps it back into an error tuple

Creates a new ok result tuple

Checks if a result_tuple is ok

Calls the next function only if it receives an error tuple. Otherwise it skips the call and returns the ok tuple. It expects the function to return a new result tuple

Converts an Ok value to an Error value if the predicate is valid

Transforms a list of result tuple to a result tuple containing either the first error tuple or an ok tuple containing the list of values

Calls the next function only if it receives an ok tuple but discards the result. It always returns the original tuple

Calls the next function only if it receives an error tuple but discards the result. It always returns the original tuple

Returns the content of an ok tuple if the value is correct. Otherwise it returns the default value

Link to this section Types

Link to this type error_tuple() View Source
error_tuple() :: {:error, any}
Link to this type ok_tuple() View Source
ok_tuple() :: {:ok, any}
Link to this type result_tuple() View Source
result_tuple() :: ok_tuple | error_tuple

Link to this section Functions

Link to this function and_then(error, function) View Source
and_then(result_tuple, (any -> result_tuple)) :: result_tuple

Calls the next function only if it receives an ok tuple. Otherwise it skips the call and returns the error tuple.

Examples

iex> business_logic = fn x -> Kaur.Result.ok(x * 2) end
...> 21 |> Kaur.Result.ok |> Kaur.Result.and_then(business_logic)
{:ok, 42}

iex> business_logic = fn x -> Kaur.Result.ok(x * 2) end
...> "oops" |> Kaur.Result.error |> Kaur.Result.and_then(business_logic)
{:error, "oops"}
Link to this function either(arg, on_error, on_ok) View Source
either(result_tuple, (any -> any), (any -> any)) :: any

Calls the first function if it receives an error tuple, and the second one if it receives an ok tuple.

Examples

iex> on_ok = fn x -> "X is #{x}" end
...> on_error = fn e -> "Error: #{e}" end
...> 42 |> Kaur.Result.ok |> Kaur.Result.either(on_error, on_ok)
"X is 42"

iex> on_ok = fn x -> "X is #{x}" end
...> on_error = fn e -> "Error: #{e}" end
...> "oops" |> Kaur.Result.error |> Kaur.Result.either(on_error, on_ok)
"Error: oops"

Creates a new error result tuple.

Examples

iex> Kaur.Result.error("oops")
{:error, "oops"}

Checks if a result_tuple is an error.

Examples

iex> 1 |> Kaur.Result.ok |> Kaur.Result.error?
false

iex> 2 |>Kaur.Result.error |> Kaur.Result.error?
true
Link to this function from_value(value) View Source
from_value(any) :: result_tuple

Promotes any value to a result tuple. It excludes nil for the ok tuples.

Examples

iex> Kaur.Result.from_value(nil)
{:error, :no_value}

iex> Kaur.Result.from_value(42)
{:ok, 42}
Link to this function keep_if(result, predicate, error_message \\ :invalid) View Source
keep_if(result_tuple, (any -> boolean), any) :: result_tuple

Converts an Ok value to an Error value if the predicate is not valid.

Examples

iex> res = Kaur.Result.ok(10)
...> Kaur.Result.keep_if(res, &(&1 > 5))
{:ok, 10}

iex> res = Kaur.Result.ok(10)
...> Kaur.Result.keep_if(res, &(&1 > 10), "must be > of 10")
{:error, "must be > of 10"}

iex> res = Kaur.Result.error(:no_value)
...> Kaur.Result.keep_if(res, &(&1 > 10), "must be > of 10")
{:error, :no_value}
Link to this function map(error, function) View Source
map(result_tuple, (any -> any)) :: result_tuple

Calls the next function only if it receives an ok tuple. The function unwraps the value from the tuple, calls the next function and wraps it back into an ok tuple.

Examples

iex> business_logic = fn x -> x * 2 end
...> 21 |> Kaur.Result.ok |> Kaur.Result.map(business_logic)
{:ok, 42}

iex> business_logic = fn x -> x * 2 end
...> "oops" |> Kaur.Result.error |> Kaur.Result.map(business_logic)
{:error, "oops"}
Link to this function map_error(data, function) View Source
map_error(result_tuple, (any -> any)) :: result_tuple

Calls the next function only if it receives an error tuple. The function unwraps the value from the tuple, calls the next function and wraps it back into an error tuple.

Examples

iex> better_error = fn _ -> "A better error message" end
...> 42 |> Kaur.Result.ok |> Kaur.Result.map_error(better_error)
{:ok, 42}

iex> better_error = fn _ -> "A better error message" end
...> "oops" |> Kaur.Result.error |> Kaur.Result.map_error(better_error)
{:error, "A better error message"}

Creates a new ok result tuple.

Examples

iex> Kaur.Result.ok(42)
{:ok, 42}

Checks if a result_tuple is ok.

Examples

iex> 1 |> Kaur.Result.ok |> Kaur.Result.ok?
true

iex> 2 |> Kaur.Result.error |>Kaur.Result.ok?
false
Link to this function or_else(data, function) View Source
or_else(result_tuple, (any -> result_tuple)) :: result_tuple

Calls the next function only if it receives an error tuple. Otherwise it skips the call and returns the ok tuple. It expects the function to return a new result tuple.

Examples

iex> business_logic = fn _ -> {:error, "a better error message"} end
...> {:ok, 42} |> Kaur.Result.or_else(business_logic)
{:ok, 42}

iex> business_logic = fn _ -> {:error, "a better error message"} end
...> {:error, "oops"} |> Kaur.Result.or_else(business_logic)
{:error, "a better error message"}

iex> default_value = fn _ -> {:ok, []} end
...> {:error, "oops"} |> Kaur.Result.or_else(default_value)
{:ok, []}
Link to this function reject_if(result, predicate, error_message \\ :invalid) View Source
reject_if(result_tuple, (any -> boolean), any) :: result_tuple

Converts an Ok value to an Error value if the predicate is valid.

Examples

iex> res = Kaur.Result.ok([])
...> Kaur.Result.reject_if(res, &Enum.empty?/1)
{:error, :invalid}

iex> res = Kaur.Result.ok([1])
...> Kaur.Result.reject_if(res, &Enum.empty?/1)
{:ok, [1]}

iex> res = Kaur.Result.ok([])
...> Kaur.Result.reject_if(res, &Enum.empty?/1, "list cannot be empty")
{:error, "list cannot be empty"}
Link to this function sequence(list) View Source
sequence([result_tuple]) :: {:ok, [any]} | {:error, any}

Transforms a list of result tuple to a result tuple containing either the first error tuple or an ok tuple containing the list of values.

Examples

iex> Kaur.Result.sequence([Kaur.Result.ok(42), Kaur.Result.ok(1337)])
{:ok, [42, 1337]}

iex> Kaur.Result.sequence([Kaur.Result.ok(42), Kaur.Result.error("oops"), Kaur.Result.ok(1337)])
{:error, "oops"}
Link to this function tap(data, function) View Source
tap(result_tuple, (any -> any)) :: result_tuple

Calls the next function only if it receives an ok tuple but discards the result. It always returns the original tuple.

Examples

iex> some_logging = fn x -> IO.puts "Success #{x}" end
...> {:ok, 42} |> Kaur.Result.tap(some_logging)
{:ok, 42}

iex> some_logging = fn _ -> IO.puts "Not called logging" end
...> {:error, "oops"} |> Kaur.Result.tap(some_logging)
{:error, "oops"}
Link to this function tap_error(data, function) View Source
tap_error(result_tuple, (any -> any)) :: result_tuple

Calls the next function only if it receives an error tuple but discards the result. It always returns the original tuple.

Examples

iex> some_logging = fn x -> IO.puts “Failed #{x}” end …> {:error, “oops”} |> Kaur.Result.tap_error(some_logging)

iex> somelogging = fn -> IO.puts “Not called logging” end …> {:ok, 42} |> Kaur.Result.tap_error(some_logging)

Link to this function with_default(arg, default_data) View Source
with_default(result_tuple, any) :: any

Returns the content of an ok tuple if the value is correct. Otherwise it returns the default value.

Examples

iex> 42 |> Kaur.Result.ok |> Kaur.Result.with_default(1337)
42

iex> "oops" |> Kaur.Result.error |> Kaur.Result.with_default(1337)
1337