What is the difference between a struct and a class in Swift?

In Swift, both struct and class are used to define complex data types. They share common features such as defining properties and methods, initializing objects through initializers, and conforming to protocols. However, there are also some important differences between struct and class.

1. Value types vs reference types: Structs are value types, while classes are reference types. When a struct is assigned to a new variable, passed as a parameter to a function, or returned by a function, its value is copied. On the other hand, when a class is assigned to a new variable or passed as a parameter to a function, its reference is copied, pointing to the same object.
2. Memory management differs between struct and class types in that instances of struct, being value types, are directly stored where they are used, while instances of class, being reference types, are allocated memory on the heap and require reference counting for memory management.
3. Inheritance: Classes can inherit properties and methods from parent classes, while structs do not support inheritance.
4. Default initializer: When all properties of a class have default values, it automatically receives a default initializer. On the other hand, a struct always generates a default initializer, regardless of whether any properties have default values.
5. Class supports type conversion and type checking operations, you can use the is and as operators to check and convert the type of an instance. In contrast, struct does not support type conversion and type checking.

In conclusion, in Swift, struct and class have different use cases. Generally speaking, if you need to share and modify objects in multiple places, you can choose to use class. However, if you only need a simple data container and want to avoid the overhead of reference counting, you can choose to use struct.