Tutorial by Examples: pt

Adapter Pattern (PHP)

A real world example using a scientific experiment where certain routines are performed on different types of tissue. The class contains two functions by default to get the tissue or routine separately. In a later version we have then adapted it using a new class to add a function that gets both. Th...

Design patterns • Adapter

Adapter (Java)

Lets assume that in your current codebase, there exists MyLogger interface like so: interface MyLogger { void logMessage(String message); void logException(Throwable exception); } Lets say that you've created a few concrete implementations of these, such as MyFileLogger and MyConsol...

Design patterns • Adapter

Subscripts

Extensions can add new subscripts to an existing type. This example gets the character inside a String using the given index: 2.2 extension String { subscript(index: Int) -> Character { let newIndex = startIndex.advancedBy(index) return self[newIndex] } } var my...

Swift Language • Extensions

Configure LintOptions with gradle

You can configure lint by adding a lintOptions section in the build.gradle file: android { //..... lintOptions { // turn off checking the given issue id's disable 'TypographyFractions','TypographyQuotes' // turn on the given issue id's enable 'Rtl...

Android • Lint Warnings

Implement Serialize for a custom map type

impl<K, V> Serialize for MyMap<K, V> where K: Serialize, V: Serialize { fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: Serializer { let mut state = serializer.serialize_map(Some(self.len()))?; ...

Rust • Serde

Implement Deserialize for a custom map type

// A Visitor is a type that holds methods that a Deserializer can drive // depending on what is contained in the input data. // // In the case of a map we need generic type parameters K and V to be // able to set the output type correctly, but don't require any state. // This is an example of a...

Rust • Serde

Verifying arguments with ArgumentCaptor

To validate arguments to methods called on a mock, use the ArgumentCaptor class. This will allow you to extract the arguments into your test method and perform assertions on them. This example tests a method which updates the name of a user with a given ID. The method loads the user, updates the na...

mockito • Getting started with mockito

Asserting on Exceptions

You can test that a function throws an exception with the built-in unittest through two different methods. Using a context manager def division_function(dividend, divisor): return dividend / divisor class MyTestCase(unittest.TestCase): def test_using_context_manager(self): ...

Python Language • Unit Testing

Parsing JavaScript Generated Page with Jsoup and HtmUnit

page.html - source code <html> <head> <script src="loadData.js"></script> </head> <body onLoad="loadData()"> <div class="container"> <table id="data" border="1"> <...

Jsoup • Parsing Javascript Generated Pages

CRTP to avoid code duplication

The example in Visitor Pattern provides a compelling use-case for CRTP: struct IShape { virtual ~IShape() = default; virtual void accept(IShapeVisitor&) const = 0; }; struct Circle : IShape { // ... // Each shape has to implement this method the same way ...

C++ • Curiously Recurring Template Pattern (CRTP)

Adapters and Consumers

Iterator methods can be broken into two distinct groups: Adapters Adapters take an iterator and return another iterator // Iterator Adapter // | | let my_map = (1..6).map(|x| x * x); println!("{:?}", my_map); Output Map { iter: 1..6 } Note that the v...

Rust • Iterators

Optimize ALV Column Width

This example shows how to optimize the column width so that column headings and data are not chopped off. alv->get_columns( )->set_optimize( ).

ABAP • ABAP GRID List Viewer (ALV)

Capturing enum values

Values passed as enum constructor arguments can be captured into variables by use of pattern matching. Assume the following enum: enum Color { RGB(r : Int, g : Int, b : Int); HSV(h : Int, s : Float, v : Float); } The red channel value can be captured as follows: var color = Color.RG...

haxe • Enums

Using :on option

The :on option lets you specify when the validation should happen. The default behavior for all the built-in validation helpers is to be run on save (both when you're creating a new record and when you're updating it). class Person < ApplicationRecord # it will be possible to update email wi...

Ruby on Rails • ActiveRecord Validations

Optional Arguments

Some procedures have optional arguments. Optional arguments always come after required arguments, but the procedure can be called without them. For example, if the function, ProcedureName were to have two required arguments (argument1, argument2), and one optional argument, optArgument3, it could b...

VBA • Procedure Calls

Overzealous except clause

Exceptions are powerful, but a single overzealous except clause can take it all away in a single line. try: res = get_result() res = res[0] log('got result: %r' % res) except: if not res: res = '' print('got exception') This example demonstrates 3 symptoms of t...

Python Language • Python Anti-Patterns

Create TypeScript project with tsconfig.json

The presence of a tsconfig.json file indicates that the current directory is the root of a TypeScript enabled project. Initializing a TypeScript project, or better put tsconfig.json file, can be done through the following command: tsc --init As of TypeScript v2.3.0 and higher this will create t...

TypeScript • tsconfig.json

DexException

com.android.dex.DexException: Multiple dex files define Lcom/example/lib/Class; This error occurs because the app, when packaging, finds two .dex files that define the same set of methods. Usually this happens because the app has accidentally acquired 2 separate dependencies on the same library....

Android • Exceptions

Parse JSON string in JavaScript

In JavaScript, the JSON object is used to parse a JSON string. This method is only available in modern browsers (IE8+, Firefox 3.5+, etc). When a valid JSON string is parsed, the result is a JavaScript object, array or other value. JSON.parse('"bar of foo"') // "bar of foo" (t...

JSON • Parsing JSON string

Using XmlAdapter to trim string.

package com.example.xml.adapters; import javax.xml.bind.annotation.adapters.XmlAdapter; public class StringTrimAdapter extends XmlAdapter<String, String> { @Override public String unmarshal(String v) throws Exception { if (v == null) return null; ...

Java Language • JAXB