Learn to type variables to various different classes. First, you can type a variable to a single class. Next, you can type a variable to a superclass, which allows any subclass to be used for the variable. Finally, you can categorize classes using interfaces. Interfaces define methods that are present with any class that implements the interface. As a result, you can type a variable to the interface and any class that follows the interface rules can be assigned to the variable.
- When you create a variable it has to have a type.…Either you define the type…or it's inferred by the value that is being assigned to it.…When you have a variable that has a type…you define the type based on a class.…Remember, since everything is a class…that means integer, Boolean, string,…and everything else that we used before…to define a variable is also a class.…So if we create a variable that accepts integers…we are typing that variable using the integer class.…
We can type variables to be any object we want,…including objects based on classes that we create ourselves.…So if I take a variable and set it to the cat type…I can create an instance of a cat class…and assign it to the variable.…But what if I wanted to assign a fish to the variable?…Because it is specifically typed to a cat…I can't take an instance of a fish class and assign it.…There is a way to deal with this.…Instead of typing to a cat…I can type the variable to the super class, animal.…
Since, by the definition of the class,…a cat and a fish are both animals…
Author
Released
11/28/2016Join Doug Winnie as he explains the principles of programming and helps you connect to core concepts by exploring three ways that programmers perform their jobs. Doug starts by sharing the history of coding and then dives into functions, values, variables, and parameters used to define actions. He covers capturing input from users, creating conditional tests, using loops with arrays, and object-oriented programming basics. He also takes you beyond programming, into processes like debugging, refactoring, and building iteratively.
- Working with values and variables
- Breaking down tasks
- Customizing functions and parameters
- Building conditional tests
- Creating and changing arrays
- Working with objects and classes
- Debugging and refactoring code
- Going beyond the code as a programmer
Skill Level Beginner
Duration
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Introduction
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Welcome1m 40s
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What you should know1m 3s
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1. Control Computers with Code
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History of programming2m 9s
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Forms of programming5m 12s
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2. Define Actions Using Code
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Break down tasks2m 29s
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Variables and scope2m 9s
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Return values from functions2m 15s
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Work with an API1m 27s
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3. Repeat Actions and Test for Conditions
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Capture input from the user3m 31s
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Create conditional tests4m 39s
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Use while loops2m 11s
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Use for loops3m 11s
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Use loops with arrays2m 5s
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4. Objects and OOP
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Everything is an object2m 21s
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Everything is a class4m 3s
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Extend classes2m 7s
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5. Beyond Programming
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Debug problems2m 50s
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Conclusion
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Next steps1m 19s
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Video: Use polymorphism using interfaces