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...
By default, the various Collection types are not thread-safe.
However, it's fairly easy to make a collection thread-safe.
List<String> threadSafeList = Collections.synchronizedList(new ArrayList<String>());
Set<String> threadSafeSet = Collections.synchronizedSet(new HashSet<S...
Given the following history, imagine you make a change that you want to squash into the commit bbb2222 A second commit:
$ git log --oneline --decorate
ccc3333 (HEAD -> master) A third commit
bbb2222 A second commit
aaa1111 A first commit
9999999 Initial commit
Once you've made your change...
The default value for an enum is zero. If an enum does not define an item with a value of zero, its default value will be zero.
public class Program
{
enum EnumExample
{
one = 1,
two = 2
}
public void Main()
{
var e =...
Now that the routes are set up, we need some way to actually change routes.
This example will show how to change routes using the template, but it is possible to change routes in TypeScript.
Here is one example (without binding):
<a routerLink="/home">Home</a>
If the user...
Python uses indentation to define control and loop constructs. This contributes to Python's readability, however, it requires the programmer to pay close attention to the use of whitespace. Thus, editor miscalibration could result in code that behaves in unexpected ways.
Python uses the colon symbo...
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...
execute the following command to insert the text into a view with a focus (if it supports text input)
6.0
Send text on SDK 23+
adb shell "input keyboard text 'Paste text on Android Device'"
If already connected to your device via adb:
input text 'Paste text on Android Device'
6...
Declaring a variable const only prevents its value from being replaced by a new value. const does not put any restrictions on the internal state of an object. The following example shows that a value of a property of a const object can be changed, and even new properties can be added, because the ob...
You can initialize a constant by using the const keyword.
const foo = 100;
const bar = false;
const person = { name: "John" };
const fun = function () = { /* ... */ };
const arrowFun = () => /* ... */ ;
Important
You must declare and initialize a constant in the same statement....
This command print all relevant application data:
version code
version name
granted permissions (Android API 23+)
etc..
adb shell dumpsys package <your.package.id>
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>
...
In all versions of Python, we can represent infinity and NaN ("not a number") as follows:
pos_inf = float('inf') # positive infinity
neg_inf = float('-inf') # negative infinity
not_a_num = float('nan') # NaN ("not a number")
In Python 3.5 and higher, we can also us...
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...
Note that some syntax elements have different behavior depending on the expression.
SyntaxDescription?Match the preceding character or subexpression 0 or 1 times. Also used for non-capturing groups, and named capturing groups.*Match the preceding character or subexpression 0 or more times.+Match th...
.encode and .decode both have error modes.
The default is 'strict', which raises exceptions on error. Other modes are more forgiving.
Encoding
>>> "£13.55".encode('ascii', errors='replace')
b'?13.55'
>>> "£13.55".encode('ascii', errors='ignore')
b'13.55'
...
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']
Class based views let you focus on what make your views special.
A static about page might have nothing special, except the template used. Use a TemplateView! All you have to do is set a template name. Job done. Next.
views.py
from django.views.generic import TemplateView
class AboutView(Tem...
Sometimes, your template need a bit more of information. For example, we would like to have the user in the header of the page, with a link to their profile next to the logout link. In these cases, use the get_context_data method.
views.py
class BookView(DetailView):
template_name = "boo...
