I am learning go and was looking at a simple go example web app: https://github.com/campoy/todo/blob/master/task/task.go
Having struct:
type Task struct {
ID int64 // Unique identifier
Title string // Description
Done bool // Is this task done?
}
and
// TaskManager manages a list of tasks in memory.
type TaskManager struct {
tasks []*Task
lastID int64
}
There are methods on the TaskManager func (m *TaskManager) Save(task *Task) error ... func (m *TaskManager) All() []*Task...
I am wondering how to generalize TaskManager into Manager, so it would have these same methods (namely: save, all, find) so it can be used on different structs, for example Users, which would all have ID field.
I assume constructing an array of general type doesn't fit because there is an ID in 'save' and 'find' methods
You'll probably want to write an interface for structures that have an ID, then generalize your Manager to operate on elements of that interface instead of elements of a specific struct.
Go doesn't have generics (for now, at least), but you still can perform what you want (not 100%) by using an interface.
type Manager interface {
Save(interface{}) error
All() ([]interface{}, error)
}
Of course, it doesn't come for free and you need to do some error handling in your TaskManager to implement the interface, example:
func (m *TaskManager) Save(t interface) error {
task, ok := t.(Task) // type assertion
if !ok {
// return error invalid input type
}
// do the rest as normal...
}
:Example for comment
type Entry interface {
SetID(int64)
GetID()int64
}
type Task struct {...}
func (t *Task) SetID(id int64) {...}
func (t *Task) GetID() {...}
func (m *TaskManager) Save(e Entry) error {...}
More info on interfaces: * http://golang.org/ref/spec#Interface_types
* http://golang.org/doc/effective_go.html#interfaces_and_types
*http://golangtutorials.blogspot.com/2011/06/interfaces-in-go.html