learngo/interfaces/05-log-parser/01-methods/changes.md

Problem

All these functions operate on a *parser value:

• main.go:
  • summarize(*p parser)
• parser.go:
  • func parse(p *parser, line string) (r result)
  • func update(p *parser, r result)
  • func err(p *parser) error

What is an object in Go?

• Object = A value of a type : &parser{} is an object.
  • type parser struct is the definition (class/blueprint) of the object.

Methods are behaviors of objects:

• Parser needs to parse, update (analyse) the parsings, and report an error if any.
• Parser also needs to summarize the results.
• So, all these functions belong to a parser object.

Solution

• Attach the functions to the parser using methods.
• Methods are the behavior of the parser.
• Keep the methods that belong to a single type in the same file.

1. Move the summarize into parser.go.
2. parser.go: Use methods.
3. main() : Use methods of the parser.

Convince

• p. shows the fields and methods belong to the parser.
• p. selects a method from the method set of the parser.
• p.method sends the p as the first parameter to the method.
• p is the receiver: *pointer. It's a pointer receiver.
• Receiver is copied to the method.