learngo/interfaces/05-log-parser/refactor-notes/refactor-01/changes.md

PROBLEM

• main.go (api client) does a lot of things:

  • read the log input
  • parse line by line
  • updates the results
  • display the results

• inflexible:

  • filter by extension (can change)
  • group by domain (can change) — group by page?

SOLUTION

• hide the parsing api from the client

• move main.go/scanner -> parser.go/parse()

  • add main.go: err handling from parse()

• parser.go/parse() -> return err directly

  • remove: if p.lerr != nil { return } from parse() and update()

  • remove: dumpErrs

  • remove: parser.go/err()

  • remove parser.go/lerr

    • return in.Err() from parse()

  • remove: p.lines++

    • return r, fmt.Errorf("line %d: %v", p.lines, err)
    • remove: lines int
    • parse() and parse() becomes:

    func parse(p *parser, line string) (result, error) {
        return parseFields(line)
    }
    
    func parse(p *parser) {
        // ...
        r, err := parse(p, in.Text())
    	if err != nil {
    		return fmt.Errorf("line %d: %v", p.lines, err)
        }
        // ...
    }
    

    • remove parse()
    • call parseFields directly in parse():

    var (
    	l  = 1
    	in = bufio.NewScanner(os.Stdin)
    )
    
    for in.Scan() {
    	r, err := parseFields(in.Text())
    	if err != nil {
    		return fmt.Errorf("line %d: %v", l, err)
    	}
    
    	update(p, r)
    	l++
    }