Tutorial by Examples: id

This validation restricts the insertion of only numeric values. class Player < ApplicationRecord validates :points, numericality: true validates :games_played, numericality: { only_integer: true } end Besides :only_integer, this helper also accepts the following options to add constrai...

This helper validates that the attribute's value is unique right before the object gets saved. class Account < ApplicationRecord validates :email, uniqueness: true end There is a :scope option that you can use to specify one or more attributes that are used to limit the uniqueness check: ...

This helper validates that the specified attributes are not empty. class Person < ApplicationRecord validates :name, presence: true end Person.create(name: "John").valid? # => true Person.create(name: nil).valid? # => false You can use the absence helper to validate th...

Use following methods if you want to skip the validations. These methods will save the object to the database even if it is invalid. decrement! decrement_counter increment! increment_counter toggle! touch update_all update_attribute update_column update_columns update_counters You ca...

class Person < ApplicationRecord validates :name, length: { minimum: 2 } validates :bio, length: { maximum: 500 } validates :password, length: { in: 6..20 } validates :registration_number, length: { is: 6 } end The possible length constraint options are: :minimum - The attribut...

First: The path structure If you don't have it you need to create the middleware folder within your app following the structure: yourproject/yourapp/middleware The folder middleware should be placed in the same folder as settings.py, urls, templates... Important: Don't forget to create the ini...

When you extend a class, you can override methods that the inherited class defines using the override keyword: public class Example { public function test():void { trace('It works!'); } } public class AnotherExample extends Example { public override function test():void ...

You can embed also a video to a webpage using the <video> element: <video width="500" height="700" controls> <source src="video.mp4" type="video/mp4"> Your browser does not support the video tag. </video>

Visual Basic has Left, Right, and Mid functions that returns characters from the Left, Right, and Middle of a string. These methods does not exist in C#, but can be implemented with Substring(). They can be implemented as an extension methods like the following: public static class StringExtens...

The normal orElse method takes an Object, so you might wonder why there is an option to provide a Supplier here (the orElseGet method). Consider: String value = "something"; return Optional.ofNullable(value) .orElse(getValueThatIsHardToCalculate()); // returns "some...

The lubridate package provides convenient functions to format date and datetime objects from character strings. The functions are permutations of LetterElement to parseBase R equivalentyyear%y, %Ym (with y and d)month%m, %b, %h, %Bdday%d, %ehhour%H, %I%pm (with h and s)minute%Msseconds%S e.g. ymd(...

C++11 In the header file: // widget.h #include <memory> // std::unique_ptr #include <experimental/propagate_const> class Widget { public: Widget(); ~Widget(); void DoSomething(); private: // the pImpl idiom is named after the typ...

<PROJECT_ROOT>\app\build.gradle is specific for app module. <PROJECT_ROOT>\build.gradle is a "Top-level build file" where you can add configuration options common to all sub-projects/modules. If you use another module in your project, as a local library you would have another...

Get width and height: var width = $('#target-element').width(); var height = $('#target-element').height(); Set width and height: $('#target-element').width(50); $('#target-element').height(100);

Get width and height: var width = $('#target-element').innerWidth(); var height = $('#target-element').innerHeight(); Set width and height: $('#target-element').innerWidth(50); $('#target-element').innerHeight(100);

Get width and height (excluding margin): var width = $('#target-element').outerWidth(); var height = $('#target-element').outerHeight(); Get width and height (including margin): var width = $('#target-element').outerWidth(true); var height = $('#target-element').outerHeight(true); Set widt...

The caption-side property determines the vertical positioning of the <caption> element within a table. This has no effect if such element does not exist. Below an example with two tables with different values set to the caption-side property: The table on the left has caption-side: top whi...

From the official documentation: Gradle. dependencies { compile "com.squareup.picasso:picasso:2.5.2" } Maven: <dependency> <groupId>com.squareup.picasso</groupId> <artifactId>picasso</artifactId> <version>2.5.2</version> </dep...

When dividing two numbers pay attention to the type you want in return. Note that dividing two integers will invoke the integer division. If your goal is to run the float division, at least one of the parameters should be of float type. Integer division: 3 / 2 # => 1 Float division 3 / 3.0 ...

By default, ui-router encodes the slash / inside parameters. If you want to send a path in the URL, you need to define a custom parameter type. Define: module.config(['$urlMatcherFactoryProvider', function($urlMatcherFactory) { $urlMatcherFactory.type('path', { decode: function(val) { retu...