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---
title: Understanding the Chain of responsability pattern
published: false
description: How to implement the design pattern "chain of responsibility"
tags: pattern
---

# Introduction

On many occasions on our projects, we find ourselves writing pieces of code that stop entirely the program or to continue given a specific condition, it can be a validation of data that was sent, a query on the database, or a logic validation of our business rules, to solve each validation we tend to write simple `ifs`, in many cases it fits well but it also starts to generate a bigger problem that is having a bunch of `ifs` on the same place will make the code harder to debug and read.

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// LOOP DE TESTE
for _, tc := range testCases {
  t.Run(tc.testName, func(t *testing.T) {
    record := Call{
      StartPeriod: tc.start,
      EndPeriod:   tc.end,
    }

    price, _ := CalcAmount(record)
    amountAsDecimal, _ := decimal.NewFromFloat(tc.expectedAmount).Float64()

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"""
This algorith convert all keys from json from camelCase to snake_case recursivily
"""

def _unpack(data):
    if isinstance(data, dict):
        return data.items()
    return data
  
def snake_case(value):

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create or replace function tipo(varchar)
	returns setof notas as
	'
		SELECT n.* FROM notas n, tiponota t
		where t.nome = $1
		and t.codigo = n.tipo_nota;
	'
language 'sql';
-- select tipo('p1');

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create table fornecedor(
	codigo integer primary key,
	razao_social varchar(100),
	telefone varchar(10)
);

create table categoria(
	codigo integer primary key,
	nome varchar(100)
);

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...
func GetPeople(w http.ResponseWriter, r *http.Request) {}
func GetPerson(w http.ResponseWriter, r *http.Request) {}
func CreatePerson(w http.ResponseWriter, r *http.Request) {}
func DeletePerson(w http.ResponseWriter, r *http.Request) {}
...

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package main

import (
    "encoding/json"
    "log"
    "net/http"
    "github.com/gorilla/mux"
)

// nossa função principal

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func main() {
    router := mux.NewRouter()
    router.HandleFunc("/contato", GetPeople).Methods("GET")
    router.HandleFunc("/contato/{id}", GetPerson).Methods("GET")
    router.HandleFunc("/contato/{id}", CreatePerson).Methods("POST")
    router.HandleFunc("/contato/{id}", DeletePerson).Methods("DELETE")
    
    log.Fatal(http.ListenAndServe(":8000", router))
}

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<?php
function generateMenu ()
{
  $array_menu = wp_get_nav_menu_items('main-menu');

  $menu    = [];
  $submenu = [];
  foreach ($array_menu as $item_menu) {
      if (empty($item_menu->menu_item_parent)) {
          $menu[$item_menu->ID] = [

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create table gravadora(
	grav_cod integer,
	grav_nome varchar(50) not null,
	grav_end varchar(100),
	constraint pk_grav primary key (grav_cod)
);

create table cd(
	cd_cod integer,
	cd_grav_cod integer,