SkollRyu / GoPractice

GoPractice

I followed Learn Go with tests to learn GO in a TDD approach

Nice hacks

In our function signature we have made a named return value (prefix string). This will create a variable called prefix in your function. This will also display in the Go Doc, so it makes things easier

func greetingPrefix(language string) (prefix string) {
	switch language {
	case french:
		prefix = frenchHelloPrefix
	case spanish:
		prefix = spanishHelloPrefix
	default:
		prefix = englishHelloPrefix
	}
	return
}

Key takeaway

1. There is a built-in testing package support

   • all test file name with xxx_test.go
   • testing.T for test state
   • testing.B for benchmark test
   • t.run to write multiple test cases within a general testing function
   • go test -cover run a coverage test

2. const for const stuff

3. var <name> <type> for variable, or <name> := <value> for shorthanded init

4. Exported names start with Capital letter; Internal start with small letter

5. variadic functions: take a variable number of arguements

   • func test (numbersToSum ...[]int) int
   • It means I can pass 1, 2, 3+ []int into the test function

6. Function is diff from method

   • method is a fucntion with a receiver
   • func (receiver receiverBase / struct) <name>() <return type>
   • func (t Type) methodName(parameter list)
   • E.g. `func (c Circle) Area() float64

7. Interface is implicit, no keyword implement

   • type <name> interface
   • once other struct implements all the methods from interface, it is already using that interface
   • Declaring interfaces so you can define functions that can be used by different types (Parametric polymorphism)

8. Table-driven test

   • Each table entry is a complete test case with inputs and expected results
   • create anonymous struct: []struct{ interface InterfaceBase ...}{{test case input, output}, {test case 2 input, output},}
   • loop over test case: for _, testCase := range testCases {...}

9. New type from existing one

   • except struct, we can create a less overkilled type
   • syntax: type <MyName> <OriginalType>
   • E.g: type Bitcoin int
   • we can also declare methods for the type

10. Pointer

    • Go copies values when you pass them to functions/methods, so if you're writing a function that needs to mutate state you'll need it to take a pointer to the thing you want to change.
    • pass a reference. Examples include referencing very large data structures or things where only one instance is necessary (like database connection pools)
    • func Add(x int) which take an integer as the parameter.
    • func AddPtr(x *int) which takes a pointer integer as the parameter.
    • AddPtr(&abc) which pass the memory address

11. nil

    • Pointers can be nil
    • When a function returns a pointer to something, you need to make sure you check if it's nil or you might raise a runtime exception - the compiler won't help you here.
    • Useful for when you want to describe a value that could be missing

12. Errors

    • Errors are the way to signify failure when calling a function/method.