Extension available for use without compilation

Question

I wanted to check if it is necessary to compile the code before using a just created extension. As a test, I created a sample extension

extension String {
    func checkExtension() {

    }
}

When I did that, neither did I save the changes in the Swift file, nor did I compile the code. But checkExtension was available for a String variable.

Query : How does SDK know without compilation, that an extension has been created and it's functions can be used in the corresponding class ?

If you create new class , are you compiling every time to access that ? — Prashant Tukadiya, May 11 '18 at 05:15
You are right, I don't. But again, the same query. How does SDK knows it is available ? — Nitish, May 11 '18 at 05:23
It is like when you type in xcode or any of tool that support programming , It knows that your syntax is correct or wrong right ? that's how it is been programmed to do so — Prashant Tukadiya, May 11 '18 at 05:26

score 0 · Accepted Answer · answered May 11 '18 at 05:58

Swift Front End Compiler takes care of that.

So Compiler is divided into Front end, and Back end.

Front End: Takes care of Lexical Analysis, Syntax analysis (parsing), Semantic analysis

Back End: Optimization, Machine Dependent optimizations, Code Generation. (sometimes analysis and optimization are called as middle end)

In Swift compiler-architecture, they are calling lexical analyser and Syntax analyser as Parser. which builds the AST(Abstract Syntax Tree). Which is used to know what belong where, and AST is used finding error when we type incorrectly and Auto Complete Etc. Simillarly swift extension works that way.

Backend comes into play when we build or Compiler our self. Which what we mostly refer to as compiler when we talk about compilers. But the fornt end is always in action in Most IDE's.

Reference : https://swift.org/compiler-stdlib/#compiler-architecture

Extension available for use without compilation

1 Answers1