How exactly does the “let” keyword work in Swift?

Question

I\'ve read this simple explanation in the guide:

The value of a constant doesn’t need to be known at compile time, but you must assign it a value exa

Answer 1

Swift properties:

Swift Properties official documentation

In its simplest form, a stored property is a constant or variable that is stored as part of an instance of a particular class or structure. Stored properties can be either variable stored properties (introduced by the varkeyword) or constant stored properties (introduced by the let keyword).

Example:

The example below defines a structure called FixedLengthRange, which describes a range of integers whose range length cannot be changed once it is created:

struct FixedLengthRange {
    var firstValue: Int
    let length: Int
}

Instances of FixedLengthRange have a variable stored property called firstValue and a constant stored property called length. In the example above, length is initialized when the new range is created and cannot be changed thereafter, because it is a constant property.