10个elixir杀手级小技巧

1. Multiple [ OR ]

# Regular Approach
find = fn(x) when x>10 or x<5 or x==7 -> x end 

# Our Hack
hell = fn(x) when true in [x>10,x<5,x==7] -> x end 

2. i( term)

Prints information about the data type of any given term. Try that in iex and see the magic.

iex> i(1..5)

Term
  1..5
Data type
  Range
Description
  This is a struct. Structs are maps with a __struct__ key.
Reference modules
  Range, Map

3. iex Custom Configuration

Save the following file as .iex.exs in your ~ home directory and see the magic.

# IEx.configure colors: [enabled: true]
# IEx.configure colors: [ eval_result: [ :cyan, :bright ] ]
IO.puts IO.ANSI.red_background() <> IO.ANSI.white() <> " ❄❄❄ Good Luck with Elixir ❄❄❄ " <> IO.ANSI.reset
Application.put_env(:elixir, :ansi_enabled, true)
IEx.configure(
 colors: [
   eval_result: [:green, :bright] ,
   eval_error: [[:red,:bright,"Bug Bug ..!!"]],
   eval_info: [:yellow, :bright ],
 ],
 default_prompt: [
   "\e[G",    # ANSI CHA, move cursor to column 1
    :white,
    "I",
    :red,
    "❤" ,       # plain string
    :green,
    "%prefix",:white,"|",
     :blue,
     "%counter",
     :white,
     "|",
    :red,
    "▶" ,         # plain string
    :white,
    "▶▶"  ,       # plain string
      # ❤ ❤-»" ,  # plain string
    :reset
  ] |> IO.ANSI.format |> IO.chardata_to_string

)

4. Custom Sigils

Each x sigil call respective sigil_x definition

defmodule MySigils do
  #returns the downcasing string if option l is given then returns the list of downcase letters
  def sigil_l(string,[]), do: String.Casing.downcase(string)
  def sigil_l(string,[?l]), do: String.Casing.downcase(string) |> String.graphemes

  #returns the upcasing string if option l is given then returns the list of downcase letters
  def sigil_u(string,[]), do: String.Casing.upcase(string)
  def sigil_u(string,[?l]), do: String.Casing.upcase(string) |> String.graphemes
end

usage

Load the module into iex

iex> import MySigils
iex> ~l/HELLO/
"hello"
iex> ~l/HELLO/l
["h", "e", "l", "l", "o"]
iex> ~u/hello/
"HELLO"
iex> ~u/hello/l
["H", "E", "L", "L", "O"]

5. Custom Error Definitions

defmodule BugError do
   defexception message: "BUG BUG .." # message is the default
end

$ iex bug_error.ex
iex> raise BugError
** (BugError) BUG BUG ..
iex> raise BugError, message: "I am Bug.."
** (BugError) I am Bug..

6. Get a Value from Nested Maps

The get_in function can be used to retrieve a nested value in nested maps using a list of keys.

nested_map = %{ name: %{ first_name: "blackode"} }     #Example of Nested Map
first_name = get_in(nested_map, [:name, :first_name])  # Retrieving the Key

# Returns nil for missing value 
nil = get_in(nested, [:name, :last_name])              # returns nil when key is not present

Read docs: Kernel.get_in/2

7. with statement

The special form with is used to chain a sequence of matches in order and finally return the result of do: if all the clauses match. However, if one of the clauses does not match, its result of the miss matched expression is immediately returned.

iex> with 1 <- 1+0,
          2 <- 1+1,
          do: IO.puts "all matched"
"all matched"
iex> with 1 <- 1+0,
          2 <- 3+1,
          do: IO.puts "all matched"
4
## since  2 <- 3+1 is not matched so the result of 3+1 is returned.

8. Writing Protocols

Define a Protocol

A Protocol is a way to dispatch to a particular implementation of a function based on the type of the parameter.
The macros defprotocol and defimpl are used to define Protocols and Protocol implementations for different types in the following example.

defprotocol Triple do    
  def triple(input)  
end  

defimpl Triple, for: Integer do    
  def triple(int) do     
    int * 3   
  end  
end   

defimpl Triple, for: List do
  def triple(list) do
    list ++ list ++ list   
  end  
end 

Usage
Load the code into iex and execute

iex> Triple.triple(3) 
9
Triple.triple([1, 2])
[1, 2, 1, 2,1,2]

9. Ternary Operator

There is no ternary operator like true ? "yes" : "no" . So, the following is suggested.

"no" = if 1 == 0, do: "yes", else: "no"

10. ????

Purposely I did not write the 1o tip. If you have one Share in the comment section below..
If you like them hit ❤