Tutorial by Examples: omp

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When a React component is created, a number of functions are called: If you are using React.createClass (ES5), 5 user defined functions are called If you are using class Component extends React.Component (ES6), 3 user defined functions are called getDefaultProps() (ES5 only) This is the firs...

componentWillReceiveProps(nextProps) This is the first function called on properties changes. When component's properties change, React will call this function with the new properties. You can access to the old props with this.props and to the new props with nextProps. With these variables, you c...

componentWillUnmount() This method is called before a component is unmounted from the DOM. It is a good place to perform cleaning operations like: Removing event listeners. Clearing timers. Stopping sockets. Cleaning up redux states. componentWillUnmount(){ ... } An example of remo...

The isEqual: method is the only reliable way to determine whether two images contain the same image data. The image objects you create may be different from each other, even when you initialize them with the same cached image data. The only way to determine their equality is to use the isEqual...

Haskell has list comprehensions, which are a lot like set comprehensions in math and similar implementations in imperative languages such as Python and JavaScript. At their most basic, list comprehensions take the following form. [ x | x <- someList ] For example [ x | x <- [1..4] ] -...

Sometimes you just need a diff to apply using patch. The regular git --diff does not work. Try this instead: git diff --no-prefix > some_file.patch Then somewhere else you can reverse it: patch -p0 < some_file.patch

In Terminal on your Mac operating system, enter the following 2 commands: lsbom -f -l -s -pf /var/db/receipts/org.nodejs.pkg.bom | while read f; do sudo rm /usr/local/${f}; done sudo rm -rf /usr/local/lib/node /usr/local/lib/node_modules /var/db/receipts/org.nodejs.*

Debug.log's second argument is always returned, so you could write code like the following and it would just work: update : Msg -> Model -> (Model, Cmd Msg) update msg model = case Debug.log "The Message" msg of Something -> ... Replacing case msg o...

Hibernate has some strategies of inheritance. The JOINED inheritance type do a JOIN between the child entity and parent entity. The problem with this approach is that Hibernate always bring the data of all involved tables in the inheritance. Per example, if you have the entities Bicycle and Mounta...

app/pipes.pipe.ts import { Pipe, PipeTransform } from '@angular/core'; @Pipe({name: 'truthy'}) export class Truthy implements PipeTransform { transform(value: any, truthy: string, falsey: string): any { if (typeof value === 'boolean'){return value ? truthy : falsey;} else return va...

Controlled form components are defined with a value property. The value of controlled inputs is managed by React, user inputs will not have any direct influence on the rendered input. Instead, a change to the value property needs to reflect this change. class Form extends React.Component { con...

Uncontrolled components are inputs that do not have a value property. In opposite to controlled components, it is the application's responsibility to keep the component state and the input value in sync. class Form extends React.Component { constructor(props) { super(props); th...

for comprehensions in Scala are just syntactic sugar. These comprehensions are implemented using the withFilter, foreach, flatMap and map methods of their subject types. For this reason, only types that have these methods defined can be utilized in a for comprehension. A for comprehension of the fo...

Comparing string in a case insensitive way seems like something that's trivial, but it's not. This section only considers unicode strings (the default in Python 3). Note that Python 2 may have subtle weaknesses relative to Python 3 - the later's unicode handling is much more complete. The first thi...

To prompt for credentials, you should almost always use the Get-Credential cmdlet: $credential = Get-Credential Pre-filled user name: $credential = Get-Credential -UserName 'myUser' Add a custom prompt message: $credential = Get-Credential -Message 'Please enter your company email address a...

This will create a composite index of both keys, mystring and mydatetime and speed up queries with both columns in the WHERE clause. CREATE INDEX idx_mycol_myothercol ON my_table(mycol, myothercol) Note: The order is important! If the search query does not include both columns in the WHERE claus...

C++11 introduced core language and standard library support for moving an object. The idea is that when an object o is a temporary and one wants a logical copy, then its safe to just pilfer o's resources, such as a dynamically allocated buffer, leaving o logically empty but still destructible and co...

Compare operation with collections - Create collections 1. Create List DescriptionJDKguavags-collectionsCreate empty listnew ArrayList<>()Lists.newArrayList()FastList.newList()Create list from valuesArrays.asList("1", "2", "3")Lists.newArrayList("1", &...

A component is some sort of user interface element, such as a button or a text field. Creating a Component Creating components is near identical to creating a window. Instead of creating a JFrame however, you create that component. For example, to create a JButton, you do the following. JButton b...