Hi, I dont need exactly an a dynamic array, i just want to create an array with fixed length in run time.  im using step 7 v15,  my main idea is something like this.

create a db with create_db function, and declare an array with fixed length in it, if i need to change the length of the array, just create an other db with a new array, and copy the values of the old array, then delete the old DB.

Is this Possible?

Thanks!!.

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Split from Variable Array Size in Step 7 V11 Basic.

Thank you for your answer, in my case i dont care the time it takes to create and delete db,  but i need to declare in the new DB an  array with UDT  data that contains struct variables. something like this

Data              array(0..newsize) of struct

    Data[0]      struct

         a           bool

         b           word

well it is just an example, the main thing is if i can to declare in the new db, the data type of my data.

MRCordova

Hi, I dont need exactly an a dynamic array, i just want to create an array with fixed length in run time. 

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Split from Variable Array Size in Step 7 V11 Basic.

 Well that could be a definition of dynamic array. 

WIKI

In computer science, a dynamic array, growable array, resizable array, dynamic table, mutable array, or array list is a random access, variable-size list data structure that allows elements to be added or removed. It is supplied with standard libraries in many modern mainstream programming languages. Dynamic arrays overcome a limit of static arrays, which have a fixed capacity that needs to be specified at allocation.

How would you address the new created DB? I mean, you can't make random structures, unless they are well  predefined with UDT,...It makes useless to create/remove DBs with several different structures. It can be done equally with fixed DB, no need to create and remove. Same rules apply: you can't have a datablock larger than certain ammount of space.

With the use of non-optimized DB, you can create a DB with data of type BYTE[N] , then you can use AT statement to declare several overlaping structures. Since these structures are known "a priori" then you get the same functionality as dynamic array.

From theory to facts:

The good thing is that it works with optimized DB access, too.

I made a structure:

RawBytes[128]

MyStruct:

  Enable : bool;

  Status : Word;

With non-optimized, the size of Mystruct would be : (bool =1 Byte) + (Word = 2 byte) = 3 bytes. With optimized access this changes. (bool =2 Byte) + (Word = 2 byte) = 4 bytes. So a max of 32 elements goes into 128 bytes of raw data.

I have compiled, indeed MyStruct: Array [0..31] of Struct compiles OK, while MyStruct: Array [0..32] of Struct gives an error, because the overlayed size is bigger than RawBytes[]