Static methods vs instance methods in C#

Question

My spark history server is failing to load because of this jquery error below.

   Uncaught RangeError: Maximum call stack size 
exceeded
    at Function.map (jquery-1.11.1.min.js:2)
    at m.fn.init.map (jquery-1.11.1.min.js:2)
    at la (jquery.dataTables.1.10.4.min.js:14)
    at HTMLTableElement.<anonymous> (jquery.dataTables.1.10.4.min.js:92)
    at Function.each (jquery-1.11.1.min.js:2)
    at m.fn.init.each (jquery-1.11.1.min.js:2)
    at m.fn.init.p [as dataTable] (jquery.dataTables.1.10.4.min.js:82)
    at m.fn.init.O.g.fn.DataTable (jquery.dataTables.1.10.4.min.js:157)
    at Object.success (historypage.js:197)
    at j (jquery-1.11.1.min.js:2)

Here is a screen shot.

I have already increased SPARK_DAEMON_MEMORY to 20G and I am using 50% CPU on my machine. Any help is greatly appreciated.

Solution 1

What do you mean by "don't get the advantages of GC"? Methods aren't garbage collected - instances are.

Virtual methods are slightly slower than non-virtual ones, and I guess there's that pesky null check before any instance method, but it's not significant. Go with the most appropriate design.

Static methods are a pain for testing though - for instance, if you authenticate in method Foo() by calling some static method, then when you're testing Foo() you can't make it just call a mock authenticator (unless the static method itself lets you do that). If you give the original instance of whatever you're testing a mock implementation of some interface containing an Authenticate() method, however, you can make it behave however you want.

EDIT: In this case, it sounds like what you really need is an instance method on your Point type to calculate the distance between two points ("this" one and another) - or potentially a static factory method on the Distance type.

Solution 2

Choosing between static and instance methods is a matter of object-oriented design. If the method you are writing is a behavior of a an object, then it should be an instance method. If it doesn't depend on an instance of an object, it should be static.

Basically, static methods belong to a type while instance methods belong to instances of a type.

Solution 3

If by being faster you mean the code inside the method is executed faster, then no. A code in a static method is just as fast as code in a non static method.

If your are talking about the overhead of performing the call to the method it becomes a little more complex. It is common for languages as Java that instance calls have more overhead. In C# this is not the case however because instance methods are not virtual by default.

So a virtual method has slightly more overhead than a non virtual method. Static methods cannot be virtual, but instance methods can be declared virtual.

As for Garbage collection, this is mainly relevant for fields, not methods. Static fields can be accessed from everywhere in the code so the garbage collector can't determine if the reference will be used again, so it is never collected.

Solution 4

Based on your example, I would write a static utility function to find the distance between two points:

public static class Geometry
{
    public static double GetDistanceBetween(Point a, Point b) { ... }
}

And then I would give Person a property called Position that returned a point. So I could write:

double distance = Geometry.GetDistanceBetween(personA.Position, personB.Position);

It's practically in English already - why make it more obscure? If you make Distance a method, then you can write:

personA.Distance(personB)

or:

personB.Distance(personA)

There's no difference between those two orderings, and yet the use of method-call syntax suggests that there might be a difference.

View more solutions

Comments

[Joan Venge]

Thanks, yeah Position is a property in my Person class. But these operations are constructed by the user via a schematic graph. So I wanted to have a unified way of doing it, but also having the ability to use them directly without creating any schematic items in the UI.

[Joan Venge]

Btw I didn't get the second part. You mean personA.Distance(personB) and Extensions.Distance is the same?

[Daniel Earwicker]

First I ask personA to work out the distance to personB, then I ask personB to work out the distance to personA. The two people are swapped. By making it a method, you imply that the person is figuring it out in their own unique, which is misleading. I'm recommending against adding a Distance method

[Daniel Earwicker]

I don't know what you mean by the user constructing the operations. Could you go into more detail in your question?

[Joan Venge]

Thanks. You mean I should have a static Distance method? Or are you talking about the instance method? Another thing to note is I am trying to have LINQ style syntax, like person.A().B().C().D() ...

[Joan Venge]

As for user making these operations, it's like these stuff is all in t he UI, so the user says for example "new person" then sets some values and add it to the UI, so I have person A, B, C, then I add a Distance item, and link it to any 2 persons. When it's executed, I have to construct it correctly

[Joan Venge]

Thanks Jon. Does it make sense now?

[Daniel Earwicker]

How complex can it get? I'm having trouble understanding why you'd need to write hard-coded expressions. The user sets up a diagram, so the relationships are all dynamic. What does it mean to "execute" it?

[Joan Venge]

So the diagram can contain an unlimited number of connections. And this Person, Distance is just an example. But say you have Add, Subtract and many many more. So in effect the graph is also not linear. It's a tree where I have to update it to shwo the final result.

[Joan Venge]

So if it was a calculator using a schematic UI, you could do stuff like perform some operations and then store it as something then pass this result to some other operation in the graph.

[Joan Venge]

Thanks Jon. I don't have distance type because it's just a float. The instance thing is where I am not sure whether to use. Like I can have the Distance method in Point, but I also want to have say PointToRGBColor, but in my design to me it seems like this RGB method should also be extension.

[Jon Skeet]

Hmm... I'm not really following the Point/RGB example. It might make sense as an extension method if it's only suitable in some contexts (rather than always, for any point, in any usage). I would advise not going too overboard with extension methods.

[Daniel Earwicker]

Right, so it almost works like a graphical expression that needs to be evaluated? Given that level of flexibility, I can't understand how you'd ever be hard-coding a chain of calls like in your "LINQ style" example. Instead your code will be looping through lists asking objects to evaluate things.

[Daniel Earwicker]

And the lists will be constructed by the user - you won't know anything definite at compile time.

[Dushan Perera]

Does it mean that for a Customer object, having an instance method like "GetAge()" and a staticmethod like "CustomerHelper.GetCustomersFromState(int stateId)" is the right way to do ?

[mmx]

GetAge makes sense as an instance method. I'm not clear on the latter though.

[Royi Namir]

@MehrdadAfshari So CustomerDAL class which has a method GetAllCustomers(..)....same as EmployeeDAL which has GetAllEmployees().....should be instance methods ? and if so - what kind of method (please supply example) should be static in those classes ?

[Zack Jannsen]

@DanielEarwicker I think you meant to say "Instance Method" where you wrote "If you make Distance a method", correct? As such the personA.Distance(person) would be acting on some local variable personA.Possition. You may wish to be verbally explicit here.