Tutorial by Examples: i

An F() object represents the value of a model field or annotated column. It makes it possible to refer to model field values and perform database operations using them without actually having to pull them out of the database into Python memory. - F() expressions It is appropriate to use F() obj...

Supposing you have setup a django project, and the settings file is in an app named main, this is how you initialize your code import os, sys # Setup environ sys.path.append(os.getcwd()) os.environ.setdefault("DJANGO_SETTINGS_MODULE", "main.settings") # Setup django imp...

Magento has a powerful set of methods to filter collections. Since there are two types of Objects that can be contained in collections, we must first determine which type of data we are working with before we can filter it. Magento implements a EAV data model for entities such as products and catego...

When we query our data, we often need more than one filter to get the exact data set we are looking for. In SQL, we handle this with AND and OR clauses. We can achieve the same thing with collections. To add an AND clause to your query, just simply add another method call. This will append the seco...

This uses the SwiftyDropbox library to upload a file from a NSFileHandle to the Dropbox account using upload sessions, handling every error case: import UIKit import SwiftyDropbox class ViewController: UIViewController { // filled in later in doUpload: var fileHandle : NSFileHandle?...

var express = require("express"), bodyParser = require("body-parser"), server = express(); //body parser for parsing request body server.use(bodyParser.json()); server.use(bodyParser.urlencoded({ extended: true })); //temperary store for `item` in memory var it...

Sample JSON: { "id": "12345", "type": "android" } Define your request: public class GetDeviceRequest { @SerializedName("deviceId") private String mDeviceId; public GetDeviceRequest(String deviceId) { this....

import curses import traceback try: # -- Initialize -- stdscr = curses.initscr() # initialize curses screen curses.noecho() # turn off auto echoing of keypress on to screen curses.cbreak() # enter break mode where pressing Enter key ...

Use the double negation syntax to check for truthiness of values. All values correspond to a boolean, irrespective of their type. irb(main):001:0> !!1234 => true irb(main):002:0> !!"Hello, world!" (irb):2: warning: string literal in condition => true irb(main):003:0> !...

You do not need to use double negation in if-else statements. if 'hello' puts 'hey!' else puts 'bye!' end The above code prints 'hey!' on the screen.

JSON (JavaScript Object Notation) is a lightweight data interchange format. Many web applications use it to send and receive data. In Ruby you can simply work with JSON. At first you have to require 'json', then you can parse a JSON string via the JSON.parse() command. require 'json' j = '{&q...

You can use JSON together with Ruby symbols. With the option symbolize_names for the parser, the keys in the resulting hash will be symbols instead of strings. json = '{ "a": 1, "b": 2 }' puts JSON.parse(json, symbolize_names: true) >> {:a=>1, :b=>2}

If you can say “YAGNI” (You ain’t gonna need it) about a feature, you better not implement it. There can be a lot of development time saved through focussing onto simplicity. Implementing such features anyway can lead to problems: Problems Overengineering If a product is more complicated than it...

Your app can't access your reminders and your calendar without permission. Instead, it must show an alert to user, requesting him/her to grant access to events for the app. To get started, import the EventKit framework: Swift import EventKit Objective-C #import <EventKit/EventKit.h> ...

Accessing the array of calendars To access the array of EKCalendars, we use the calendarsForEntityType method: Swift let calendarsArray = eventStore.calendarsForEntityType(EKEntityType.Event) as! [EKCalendar] Iterating through calendars Just use a simple for loop: Swift for calendar in cale...

Creating the event object Swift var event = EKEvent(eventStore: eventStore) Objective-C EKEvent *event = [EKEvent initWithEventStore:eventStore]; Setting related calendar, title and dates Swift event.calendar = calendar event.title = "Event Title" event.startDate = startDate /...

In Symfony, the built-in ChoiceType (and EntityType or DocumentType extending it), basicaly work with a constant choice list. If you want to make it work with ajax calls, you have to change them to accept any sumitted extra choices. How to start with an empty choice list ? When you build your...

This is an example to show how to change the allowed choices on a subCategory select field depending on the value of the category select field. To do that you have to make your subCategory choices dynamical for both client and server side. 1. Make the form dynamic on the client side for display / ...

In Ruby, there is always an implicit receiver for all method calls. The language keeps a reference to the current implicit receiver stored in the variable self. Certain language keywords like class and module will change what self points to. Understanding these behaviors is very helpful in mastering...

When you define a class or module, the implicit receiver becomes a reference to the class itself. For example: puts "I am #{self}" class Example puts "I am #{self}" end Executing the above code will print: "I am main" "I am Example"