Join Scott Gardner for an in-depth discussion in this video Use type checking and casting operators, part of Swift 3 Essential Training: Beyond the Basics.
- [Narrator] Swift includes the is and as operators,…which are used frequently when working with classes.…I'm starting out with two class definitions.…Class A is a base class.…That is, it doesn't inherit from another class.…Class B inherits from class A.…I've also created instances of these two classes.…I'll add these two instances to an array,…and because class B inherits from class A,…the array's type will be inferred to be class A.…
After all, class B is a more specialized version of class A.…I can work with both elements in array…as instances of class A and access their A value values.…But if I try to work with the last element…as a class B instance, which I know it actually is,…I'll get an error.…Value of type class A has no member B value.…This is because it is currently being casted…as an instance of class A.…
I'll comment that out for now.…I'll use the is operator to check…if it is a class B instance.…And if I want to downcast it as a class B instance,…I can use the as operator.…There are two ways to do this.…
- Adding source files, resources, links, and literals
- Adding pages to a playground
- Using overflow operators and bitwise operators
- Using ranges with strings
- Creating complex sequences
- Chaining higher-order functions
- Defining lazy properties
- Using failable initializers
- Mutating methods
- Working with singletons
- Nesting function types
- Creating error types and recursive enumerations
- Extending concrete types
- Referencing selectors and key paths
- Working with protocol-oriented programming
- Defining class-only protocols and optional protocols
- Using option sets, type checking, and casting operators
Skill Level Intermediate
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iOS App Development: Test-Driven Developmentwith Harrison Ferrone2h 14m Intermediate
3. Strings and Characters
4. Sequences and Collections
5. Control Flow
6. Value and Reference Types
9. Access Control
Understand access control3m 47s
Next steps1m 2s
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