Best practice: ordering of public/protected/privat

Question

I am starting a new project from the ground up and want it to be clean / have good coding standards. In what order do the seasoned developers on here like to lay things out within a class?

A : 1) public methods 2) private methods 3) public vars 4) private vars

B : 1) public vars 2) private vars 3) public methods 4) private methods

C : 1) public vars 2) public methods 3) private methods 4)private vars

I generally like to put public static vars at the top, but then would a public static method be listed ahead of your constructor, or should the constructor always be listed first? That sort of thing...

I know it's finnicky but I just wondered: what are best practices for this?

PS: no I don't use Cc#. I know. I'm a luddite.

Answer 1

The best practice is to be consistent.

Personally, I prefer putting public methods first, followed by protected methods, following by private methods. Member data should in general always be private or protected, unless you have a good reason for it not to be so.

My rationale for putting public methods at the top is that it defines the interface for your class, so anyone perusing your header file should be able to see this information immediately.

In general, private and protected members are less important to most people looking at the header file, unless they are considering modifying the internals of the class. Keeping them "out of the way" ensures this information is maintained only on a need to know basis, one of the more important aspects of encapsulation.

Answer 2

Some editors, like Eclipse and its offspring, allow you to reorder in the outline view the the vars and the methods, alphabetically or as in page.

Answer 3

I think I have a different philosophy on this than most. I prefer to group related items together. I can't stand having to jump around to work with a class. The code should flow and using a rather artificial ordering based on accessibility (public, private, protected etc. ) or instance versus static or member versus property versus function doesn't help keep a nice flow. So if I nave a public method Method that is implemented by private helper methods HelperMethodA, HelperMethodB etc. then rather than have these method far apart from each other in the file, I will keep them close to each other. Similarly, if i have an instance method that is implemented by a static method, I will group these together too.

So my classes often look like this:

class MyClass {
    public string Method(int a) {
        return HelperMethodA(a) + HelperMethodB(this.SomeStringMember);
    }

    string HelperMethodA(int a) { // returns some string }

    string HelperMethodB(string s) { // returns some string }

    public bool Equals(MyClass other) { return MyClass.Equals(this, other); }

    public static bool Equals(MyClass left, MyClass right) { // return some bool }

    public double SomeCalculation(double x, double y) {
        if(x < 0) throw new ArgumentOutOfRangeException("x");
        return DoSomeCalculation(x, y); 
    }

    const double aConstant;
    const double anotherConstant;
    double DoSomeCalculation(double x, double y) {
        return Math.Pow(aConstant, x) * Math.Sin(y) 
            + this.SomeDoubleMember * anotherConstant;
    }       
}

Answer 4

This would be my ordering

1. Static Variables
2. Static Methods
3. Public Variables
4. Protected Variables
5. Private Variables
6. Constructors
7. Public Methods
8. Protected Methods
9. Private Methods

I use the following rules:

• static before anything
• variables before constructors before methods (i consider constructors to be in the category of methods)
• public before protected before private

The idea is that you define the object (the data), before the behaviours (methods). Statics need to be separated because they aren't really part of the object, nor it's behaviour.