The API #3 – UPDATE (UPDATE/PUT)

To UPDATE a record is a 2 part task. Populate form. Update a record using JSON.

1-8. Get data and fill the form

The first 8 steps are similar to the READ process. The difference is that the data should fill the form "dynamically".

function api3fill(path) {
  var url = "https://api3.go4webdev.org/"+path;
  var xhr = new XMLHttpRequest();
  xhr.open("GET", url);
  xhr.responseType = 'json';
  xhr.onload = function() {
    if (xhr.readyState === 4) {
      fillform(this.response)
    }
  };
  xhr.send();
}

function fillform(data) {
  const {
    elements
  } = document.querySelector('form')
  for (const [key, value] of Object.entries(data)) {
    const field = elements.namedItem(key)
    if (field) field.value = value
  }
}

9. Edit record

10+11. Extract JSON and send via AJAX POST Request

This function extract the JSON from the HTML form and send this to the API

function api3update(elem, event) {
  event.preventDefault();
  
  //get JSON values from form
  var form = elem;
  var formData = new FormData(form)
  var object = {};
  formData.forEach(function(value, key) {
    object[key] = value;
  });
  var path = object.path
  var json = JSON.stringify(object)
  
  //call API
  var url = "https://api3.go4webdev.org/" + path;
  var xhr = new XMLHttpRequest();
  xhr.open("PUT", url);
  xhr.setRequestHeader("Accept", "application/json");
  xhr.send(json);
}

12+13. Lookup and get SQL Query from the REST call

The Go API first get the desired SQL Query from Postgresql lookup database.

func Getquery(path string) string {
  // get query from lookup db
  var query string
  err := db.QueryRow("SELECT sql_query FROM sqls WHERE sql_id=$1", path).Scan(&query)
  if err != nil {
    path = ""
  }
  fmt.Println(query)
  return query
}

The lookup Query look like this with a parameter $1 that is filled with JSON from the form previously.

WITH list AS 
(SELECT * FROM json_populate_record
(null::tsk,$1))
UPDATE tsk
SET (tsk_subject,tsk_desc) = (SELECT tsk_subject,tsk_desc FROM list) 
WHERE tsk_id=(SELECT tsk_id FROM list)

14+15. Execute the SQL Query

The PUT endpoint in the Go API looks like this:

package main

import (
  "io/ioutil"
  "net/http"
  "net/url"
)

func Update(w http.ResponseWriter, r *http.Request) {
  body, err := ioutil.ReadAll(r.Body)

  if err != nil {
    log(err.Error())
  }

  scope, action, val := getpath(r)

  val = string(body)
  val, _ = url.QueryUnescape(val)

  switch action {
  case "edit":
    query := Getquery(scope + "_" + action)
    edit(query, val)
  }
}

// edit record
func edit(query string, val string) {
  db.MustExec(query, val)
}