Tutorial by Examples: el

Alternative if/else statement

<?php if ($condition): do_something(); elseif ($another_condition): do_something_else(); else: do_something_different(); endif; ?> <?php if ($condition): ?> <p>Do something in HTML</p> <?php elseif ($another_condition): ?> <p>...

PHP • Alternative Syntax for Control Structures

Hello World

See how to compile this code in Initialize and build import Html main = Html.text "Hello World!"

Elm Language • Getting started with Elm Language

Delegate and Datasource

The UITableViewDelegate is used to control how the table is displayed, and UITableViewDataSource is used to define the UITableView's data. There are two required methods and many optional ones which can be used to customize size, sections, headings, and cells in the UITableView. UITableViewDataSo...

iOS • UITableView

Overlapping Elements with z-index

To change the default stack order positioned elements (position property set to relative, absolute or fixed), use the z-index property. The higher the z-index, the higher up in the stacking context (on the z-axis) it is placed. Example In the example below, a z-index value of 3 puts green on to...

CSS • Positioning

Relative Position

Relative positioning moves the element in relation to where it would have been in normal flow .Offset properties: top left right bottom are used to indicate how far to move the element from where it would have been in normal flow. .relpos{ position:relative; top:20px; left:3...

CSS • Positioning

Don't Repeat Yourself (DRY)

To help to maintain clean code, Rails follows the principle of DRY. It involves whenever possible, re-using as much code as possible rather than duplicating similar code in multiple places (for example, using partials). This reduces errors, keeps your code clean and enforces the principle of writin...

Ruby on Rails • Rails Best Practices

Remove, delete and cleanup containers

docker rm can be used to remove a specific containers like this: docker rm <container name or id> To remove all containers you can use this expression: docker rm $(docker ps -qa) By default docker will not delete a container that is running. Any container that is running will produce a...

Docker • Managing containers

Hello World

Without JSX Here's a basic example that uses React's main API to create a React element and the React DOM API to render the React element in the browser. <!DOCTYPE html> <html> <head> <meta charset="UTF-8" /> <title>Hello React!</title> ...

React • Getting started with React

Hello World

class Greeter { greeting: string; constructor(message: string) { this.greeting = message; } greet(): string { return this.greeting; } }; let greeter = new Greeter("Hello, world!"); console.log(greeter.greet()); Here we have a class, Gree...

TypeScript • Getting started with TypeScript

ModelForm Example

Create a ModelForm from an existing Model class, by subclassing ModelForm: from django import forms class OrderForm(forms.ModelForm): class Meta: model = Order fields = ['item', 'order_date', 'customer', 'status']

Django • Forms

Change list

Let's say you have a simple myblog app with the following model: from django.conf import settings from django.utils import timezone class Article(models.Model): title = models.CharField(max_length=70) slug = models.SlugField(max_length=70, unique=True) author = models.ForeignKe...

Django • Administration

Creating a model with relationships

Many-to-One Relationship from django.db import models class Author(models.Model): name = models.CharField(max_length=50) #Book has a foreignkey (many to one) relationship with author class Book(models.Model): author = models.ForeignKey(Author, on_delete=models.CASCADE) publish_...

Django • Models

Using custom deleters to create a wrapper to a C interface

Many C interfaces such as SDL2 have their own deletion functions. This means that you cannot use smart pointers directly: std::unique_ptr<SDL_Surface> a; // won't work, UNSAFE! Instead, you need to define your own deleter. The examples here use the SDL_Surface structure which should be fre...

C++ • Smart Pointers

Writing a lens without Template Haskell

To demystify Template Haskell, suppose you have data Example a = Example { _foo :: Int, _bar :: a } then makeLenses 'Example produces (more or less) foo :: Lens' (Example a) Int bar :: Lens (Example a) (Example b) a b There's nothing particularly magical going on, though. You can write ...

Haskell Language • Lens

Example tests (self documenting tests)

This type of tests make sure that your code compiles properly and will appear in the generated documentation for your project. In addition to that, the example tests can assert that your test produces proper output. sum.go: package sum // Sum calculates the sum of two integers func Sum(a, b in...

Go • Testing

Basic selectors

SelectorDescription*Universal selector (all elements)divTag selector (all <div> elements).blueClass selector (all elements with class blue).blue.redAll elements with class blue and red (a type of Compound selector)#headlineID selector (the element with "id" attribute set to headline)...

CSS • Selectors

Simple queries on a standalone model

Here is a simple model that we will use to run a few test queries: class MyModel(models.Model): name = models.CharField(max_length=10) model_num = models.IntegerField() flag = models.NullBooleanField(default=False) Get a single model object where the id/pk is 4: (If there are no...

Django • Querysets

Custom user model with email as primary login field.

models.py : from __future__ import unicode_literals from django.db import models from django.contrib.auth.models import ( AbstractBaseUser, BaseUserManager, PermissionsMixin) from django.utils import timezone from django.utils.translation import ugettext_lazy as _ class UserManage...

Django • Extending or Substituting User Model

Ghost element technique (Michał Czernow's hack)

This technique works even when the container's dimensions are unknown. Set up a "ghost" element inside the container to be centered that is 100% height, then use vertical-align: middle on both that and the element to be centered. CSS /* This parent can be any width and height */ .block...

CSS • Centering

Deleting

You can delete data after writing it to the database. You can either delete a model instance if you have retrieved one, or specify conditions for which records to delete. To delete a model instance, retrieve it and call the delete() method: $user = User::find(1); $user->delete(); Alternat...

Laravel • Eloquent