Speed, portability and permanence also make aerosol paint a common graffiti medium. In the late 1970s, street graffiti writers' signatures and murals became more elaborate and a unique style developed as a factor of the aerosol medium and the speed required for illicit work. Many now recognize graffiti and street art as a unique art form and specifically manufactured aerosol paints are made for the graffiti artist. A stencil protects a surface, except the specific shape to be painted. Stencils can be purchased as movable letters, ordered as professionally cut logos or hand-cut by artists.
Decorator Abstractions: A decorator abstraction is an abstract class that implements the component interface. Critically, the decorator abstraction must also contain a pointer to some instance of the same interface. Inside the decorator abstraction, each of the component interface behaviors will be delegated to whichever concrete component the pointer indicates.
Here we ensure that the key student_id is part of the request. Although this validation works, it really does not belong in the function itself. Plus, perhaps there are other routes that use the exact same validation. So, let’s keep it DRY and abstract out any unnecessary logic with a decorator. The following @validate_json decorator will do the job:
Now we have our logit decorator in production, but when some parts of our application are considered critical, failure might be something that needs more immediate attention. Let’s say sometimes you want to just log to a file. Other times you want an email sent, so the problem is brought to your attention, and still keep a log for your own records. This is a case for using inheritence, but so far we’ve only seen functions being used to build decorators.
The first example of modernism in painting was impressionism, a school of painting that initially focused on work done, not in studios, but outdoors (en plein air). Impressionist paintings demonstrated that human beings do not see objects, but instead see light itself. The school gathered adherents despite internal divisions among its leading practitioners, and became increasingly influential. Initially rejected from the most important commercial show of the time, the government-sponsored Paris Salon, the Impressionists organized yearly group exhibitions in commercial venues during the 1870s and 1880s, timing them to coincide with the official Salon. A significant event of 1863 was the Salon des Refusés, created by Emperor Napoleon III to display all of the paintings rejected by the Paris Salon.
NOTE A Property Descriptor is not provided as an argument to a property decorator due to how property decorators are initialized in TypeScript. This is because there is currently no mechanism to describe an instance property when defining members of a prototype, and no way to observe or modify the initializer for a property. The return value is ignored too. As such, a property decorator can only be used to observe that a property of a specific name has been declared for a class.
When we instantiate a SimpleMessage and then pass it to the various decorators, we now get new behavior. Moreover, since both the concrete component and the concrete decorators all implement / descend from IMessage, they are interchangeable as far as the program is concerned, meaning that we can loop over them together. Further, rather than having to create a new ExcitedAndQuizzicalMessageDecorator class, we were able to achieve the same effect by double wrapping a SimpleMessage object (first in an ExcitedMessageDecorator and then in a QuizzicalMessageDecorator). Finally, note that despite having been passed into various decorators, our simpleMsg object remains unchanged at the end of the program.
Abstract painting uses a visual language of form, colour and line to create a composition that may exist with a degree of independence from visual references in the world. Abstract expressionism was an American post-World War II art movement that combined the emotional intensity and self-denial of the German Expressionists with the anti-figurative aesthetic of the European abstract schools—such as Futurism, Bauhaus and Cubism, and the image of being rebellious, anarchic, highly idiosyncratic and, some feel, nihilistic.
In this snippet we have a class hierarchy with a SimpleMessage at the top. The SimpleMessage class has a constructor that accepts a content string as well as two methods: GetMessage; and, PrintMessage. Down the hierarchy we have three subclasses: ExcitedMessage; QuizzicalMessage; and, ExcitedAndQuizzicalMessage. The only difference in the subclasses is that they override the SimpleMessage constructor to change the content string and append various exclamations. When we instantiate various message objects, using the same content string, and iterate over them, each has their own unique output.
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