Using BaseArrays [SOLVED]

On 11/01/2015 at 12:12, xxxxxxxx wrote:

User Information:
Cinema 4D Version:   R16 
Platform:   Windows  ;   
Language(s) :

So I'm transitioning a completed python plugin to C++ and C++ doesn't have easy to use dictionaries like Python. Or at least know that Maxon recommends I use in their best coding practices. That's fine, I can use a BaseArray. The question is how does one initialize a BaseArray with a set of known values.  A second part to that would be how I might use a resource of some sort to load a BaseArray with values.

On 11/01/2015 at 13:57, xxxxxxxx wrote:

In C++ dictionaries are called maps.
These are the R14 examples I have in my notes.
I haven't used these in R16 yet. So the code might need to written slightly different. But hopefully it will give you a quick boost in using them.

//The HashMap array in R14++ is similar to a dictionary  
//Each array element has a key, and a value  
//The key can be used to look up the elements in the array. Instead of using element index numbers  
//The key and value types must bet set up when creating the HM:  maxon::HashMap<type, type> myHmap;  
//NOTE: You can use HM->put to add new items to the array if you don't want to check if an entry already exists  
Example #1   
  maxon::HashMap<Int, String> myHmap;  
  auto entry1 = myHmap.Put(1, "first");  // 1 is the key    "first" is the value  
  auto entry2 = myHmap.Put(2, "second"); // 2 is the key    "second" is the value  
  GePrint(myHmap.FindEntry(2)->GetValue()); //Find using the key (which is 2 in this example)  
Example #2  
  maxon::HashMap<Int, Float> myHmap;  
  auto entry1 = myHmap.Put(1, 5.5);  // 1 is the key    5.5 is the value  
  auto entry2 = myHmap.Put(2, 22.4); // 2 is the key    22.4 is the value  
  GePrint(String::FloatToString( myHmap.FindEntry(2)->GetValue())); //Find using the key (which is 2 in this example)  
//This is an example of filling a HashMap with Atom objects as the keys  
//Then assigning String values to them  
  BaseObject *obj1 = doc->GetFirstObject();  
  if(!obj1) return false;  
  BaseObject *obj2 = obj1->GetNext();  
  if(!obj2) return false;  
  //Create a HashMap array and insert the two objects into it. And set their values as text  
  //The key values lets us look up the items in the HashMap array  
  maxon::HashMap<C4DAtom*, String> myHmap;  
  maxon::Bool created = false;  
  auto entry1 = myHmap.FindOrCreateEntry(obj1, created);      
  if(created) entry1->SetValue("first");  
  auto entry2 = myHmap.FindOrCreateEntry(obj2, created);  
  if(created) entry2->SetValue("second");  
  //Iterate through the HM array using an iterator  
  //The iterator 'it' is the value of each array element  
  for(auto it = myHmap.Begin(); it != myHmap.End(); ++it)  
      auto value = it;  
      Int32 t = it->GetKey()->GetType();  //Get the type of object in the HM array  
      String keyVal = it->GetValue();     //Get the key value in the HM for this object  
      //We can change the keys in the HashMap if we want  
      if (keyVal == "first") entry1->SetValue("newKeyValue");  
      GePrint(String::IntToString(t) + "  " + keyVal);  
  //Print the new key value in the HashMap  


On 11/01/2015 at 16:16, xxxxxxxx wrote:

As always thanks Scott. I saw that the standard library had maps, but I didn't know the SDK had one too. That's solid, I'll try it out.

On 11/01/2015 at 19:36, xxxxxxxx wrote:

I appear to have ran into another problem. Apparently the maxon string class isn't supported as a key?

Error 1 error C2039: 'GetHashCode' : is not a member of 'String'

On 12/01/2015 at 14:02, xxxxxxxx wrote:

Just documenting my progress for anyone else who stumbles on this. I did a workaround by using char* as the key, but FindEntry isn't matching up the char strings, still looking into that.

On 13/01/2015 at 13:27, xxxxxxxx wrote:

Hi eldiren,

Here's some info that I think can help you with the problems you're having with C4D's hash code:

Link in help to GetHashCode() call, takes a const Char* key and returns a static UInt:

Link to GetHashCode() call

Example code to create a C-String from C4D's String class:

// Create a char* null terminated C-string from a C4D String  
size_t keyLength = keyString.GetCStringLen(STRINGENCODING_8BIT);  
char* keyCharString = new char[keyLength + 1];  
keyString.GetCString(keyCharString, keyLength + 1, STRINGENCODING_8BIT);  
// Get the hash code using keyCharString  
UInt hashCode = GetHashCode(keyCharString);  
// *** Use the hashCode value here  
// Delete the string when you're done, or you'll leak memory  
delete [] keyCharString;  
keyCharString = nullptr;  

I hope that helps!

Joey Gaspe
SDK Support Engineer

On 13/01/2015 at 17:10, xxxxxxxx wrote:

@j_gaspe Thanks for that. That's kinda what I ended up coming up with. In my put functions for the HashMap I used GetHashCode to hash the strings. Then I basically had to take to take the GetName function of a BaseObject and run GetHashCode on that and then compare it to my keys using HashMap's FindEntry function. Roundabout but it got the job done.

On 14/01/2015 at 06:38, xxxxxxxx wrote:

Hi eldiren,

Thanks for letting me know it worked out.  I'll close the topic as being solved.

Joey Gaspe
SDK Support Engineer