Tutorial by Examples: le

<?php use yii\db\Migration; class m150101_185401_create_news_table extends Migration { public function up() { } public function down() { echo "m101129_185401_create_news_table cannot be reverted.\n"; return false; } /* // Use safeUp/safeDown to run migra...

public function up() { $this->dropTable('post'); }

yii migrate/create create_post_table --fields="title:string,body:text" Generates: /** * Handles the creation for table `post`. */ class m150811_220037_create_post_table extends Migration { /** * @inheritdoc */ public function up() { $this->createTable('post', [ ...

public function up() { $this->createTable('post', [ 'id' => $this->primaryKey() ]); }

By default, migrations are applied to the same database specified by the db application component. If you want them to be applied to a different database, you may specify the db command-line option like shown below: yii migrate --db=db2

AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder( MainActivity.this); alertDialogBuilder.setTitle("Title Dialog"); alertDialogBuilder .setMessage("Message Dialog") .setCancelable(true) ...

SELECT * FROM table1, table2 SELECT table1.column1, table1.column2, table2.column1 FROM table1, table2 This is called cross product in SQL it is same as cross product in sets These statements return the selected columns from multiple tables in one query....

You can call a function in Racket by wrapping it in parentheses with the arguments after it. This looks like (function argument ...). > (define (f x) x) > (f 1) 1 > (f "salmon") "salmon" > (define (g x y) (string-append x y)) > (g "large" "sal...

Basics A tuple is an ordered, finite list of elements. Tuples are commonly used in programming as a means to work with one single entity collectively instead of individually working with each of the tuple's elements, and to represent individual rows (ie. "records") in a relational databa...

AlertDialog.Builder builder = new AlertDialog.Builder(context); //Set Title builder.setTitle("Reset...") //Set Message .setMessage("Are you sure?") //Set the icon of the dialog .setIcon(drawable) //Set...

Imagine you have the following HTML: <div> <label>Name:</label> John Smith </div> And you need to locate the text "John Smith" after the label element. In this case, you can locate the label element by text and then use .next_sibling property: from ...

BeautifulSoup has a limited support for CSS selectors, but covers most commonly used ones. Use select() method to find multiple elements and select_one() to find a single element. Basic example: from bs4 import BeautifulSoup data = """ <ul> <li class="item&quo...

.SD .SD refers to the subset of the data.table for each group, excluding all columns used in by. .SD along with lapply can be used to apply any function to multiple columns by group in a data.table We will continue using the same built-in dataset, mtcars: mtcars = data.table(mtcars) # Let's not ...

Sometimes it is appropriate to use an immutable empty collection. The Collections class provides methods to get such collections in an efficient way: List<String> anEmptyList = Collections.emptyList(); Map<Integer, Date> anEmptyMap = Collections.emptyMap(); Set<Number> anEmptySe...

In Julia, the @show macro is often useful for debugging purposes. It displays both the expression to be evaluated and its result, finally returning the value of the result: julia> @show 1 + 1 1 + 1 = 2 2 It is straightforward to create our own version of @show: julia> macro myshow(exp...

Sometimes you want to add an element to the beginning of an array without modifying any of the current elements (order) within the array. Whenever this is the case, you can use array_unshift(). array_unshift() prepends passed elements to the front of the array. Note that the list of elements is ...

The @var keyword can be used to describe the type and usage of: a class property a local or global variable a class or global constant class Example { /** @var string This is something that stays the same */ const UNCHANGING = "Untouchable"; /** @var string $some_s...

Once registered a dependency can be retrieved by adding parameters on the Controller constructor. // ... using System; using Microsoft.Extensions.DependencyInjection; namespace Core.Controllers { public class HomeController : Controller { public HomeController(ITestServic...

Haskell is a pure language, meaning that expressions cannot have side effects. A side effect is anything that the expression or function does other than produce a value, for example, modify a global counter or print to standard output. In Haskell, side-effectful computations (specifically, those wh...

For Addition "4" + 2 # Gives "42" 4 + "2" # Gives 6 1,2,3 + "Hello" # Gives 1,2,3,"Hello" "Hello" + 1,2,3 # Gives "Hello1 2 3" For Multiplication "3" * 2 # Gives "33" 2 * "3&quot...