What is dynamic type?
Generated on 9/30/2024
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Dynamic type in the context of programming languages like Swift refers to the ability of a program to determine the type of an object at runtime rather than at compile time. This is often associated with dynamic dispatch, which is a mechanism that allows a program to select which method or function to call at runtime based on the type of the object.
In Swift, dynamic dispatch is used to enable polymorphism and other powerful tools for abstraction. For example, if a method is declared in the main body of a protocol, it is a protocol requirement, and calls to it use dynamic dispatch. However, if the method is declared in a protocol extension, the call uses static dispatch, which is more efficient because it allows for compile-time optimizations like inlining and generic specialization.
Dynamic types are also relevant when discussing memory layout and allocation. Swift can handle types whose size is determined at runtime, which is necessary for certain value types in the SDK that may change their stored properties in future OS updates. This flexibility allows Swift to efficiently manage memory even when the exact layout of a type is not known at compile time.
For more details on how Swift handles dynamic dispatch and dynamically-sized types, you can refer to the session Explore Swift performance (21:08).
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