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DarkBASIC Professional Discussion / How can I pass a user defined type to a function.

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Jester1958
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Posted: 22nd Feb 2014 23:14
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I am writing a game program and I need to pass user defined types to a function. However, it seems that DB Pro will only allow you to pass Base types (ie. Integers, strings, Real, etc.). Can anybody tell me how to work around this problem?

The First, The Original, The only True CYBER_JESTER!
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WickedX
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Posted: 23rd Feb 2014 06:10
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Dark Basic Professional will allow passing udt to a function. Although in the function you are not allowed to alter the udt outside of the functions local copy. To solve this, you can make the udt global or make it a udt array, either way you no longer even need to pass it to the function as a parameter.
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Phaelax
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Posted: 23rd Feb 2014 07:23
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You pass it the same way as you do any other primitive data type, but you must define the function parameters.



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ShellfishGames
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Posted: 23rd Feb 2014 11:58
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Quote: "You pass it the same way as you do any other primitive data type, but you must define the function parameters."


Indeed, but as WickedX said this will only give the function access to a local copy of the udt variable. So you can read its content, but not alter the variable originally passed to the function. I'm also not sure about performance, if DBPro really copies all the values defined in the UDT it might get rather slow for complex types.

I personally prefer the method of storing my udt variables within arrays (such as "dim Unit(UnitCount) as Unit_Type") and pass the array ID to any function that is meant to manipulate the variable.

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tiffer
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Posted: 24th Feb 2014 02:32
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IMO you wouldn't. If it's that sort of task that shares variables sterhouldn't it be a subroutine? Functions are designed to be called interchangeably so giving them access to variables could pose problems.

Cwatson
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Phaelax
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Posted: 24th Feb 2014 05:13
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Quote: "Indeed, but as WickedX said this will only give the function access to a local copy of the udt variable."

It's the same for passing any other variable, he never said he needed to pass it by reference.

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Green Gandalf
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Posted: 24th Feb 2014 11:33
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Quote: "It's the same for passing any other variable, he never said he needed to pass it by reference."


Indeed.



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Jester1958
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Posted: 1st Mar 2014 16:14
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Thank you VERY much. I will let you know if this solves the problem.
BTW - The function does need to change the value of certain fields in the UDT, and then pass these new values onto a validation function to see if they are allowed.

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Mobiius
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Posted: 1st Mar 2014 22:31
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UDTs are typed arrays, why not simply pass the index to the array and use it that way?

This would be an example...




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Phaelax
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Posted: 1st Mar 2014 23:06
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A UDT doesn't have to be an array. I've done so many times as just a better way to organize variables for a particular system.

But in this case, if he is using an array then yes I agree passing the index would be the best choice.

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