typedef struct vs. Object - Benefits

Question

I plan to define a class, that among its properties contains coordinates for an x/y grid. However, I'm unsure of the 'best' way to approach the design of this. It's a very simple issue, I just want to do it correctly and have a justification!

One solution would be to have to two properties, of type 'int', one for x and one for y, within the object.

The other would be define a typedef struct of two ints containing x/y values and naming it <ClassPrefix>Coordinate. Similar to CGSize?

Are there any other/better ways to do this? Which is preferred? Not sure how to justify either way.

Thanks!

Tim.

Answer 1

It is a trade off.

A class and its instances will cost more in resource, especially when you have to make a lot of them. If there will not be so many instances, it is not a problem.

Structure is faster but it's difficult to extent and the most inconvenient thing is a struct can not hold objects or method.

For your example, if you just use it for coordinates, I suggest you to use struct. But it depends on your design and code. There is no absolute judgment which is best.

Answer 2

The answer to the "Which one is preferred?" question depends on a few factors:

• How many items like this you plan to create? - If the answer is "millions", struct wins; if the answer is "fifty eight", object wins.
• Do you need to define methods on it? - If the answer is "yes", object wins; otherwise, struct may be OK.
• Do you plan to define arrays of it? - If the answer is "yes", struct may be a better choice.
• Do you need to create and destroy it often? - If the answer is "yes", struct may be a better choice.

Ultimately, your design constraints help you determine what's best; there is no data structure that is universally "better".

Answer 3

In addition to @dasblinkenlight answer, I'll give you some decision advices:

• Is the structure immutable after creation?
  Use an object.

• Does the structure owns (= retains) pointers to other objects or arrays (both C arrays or NSArray)? Does it interact with objects (= has methods with object parameters)?
  Then use an object.

• Does the structure contains only primitive types (int, float, other structs etc) and it interacts only with other primitives/structs?
  Then use a struct with functions.