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1 class ComponentBase(object):
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2 """Component abstract base class
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3
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4 Strictly speaking you do not need to derive from this class to create your
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5 own components, but it does serve to document the full interface that a
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6 component implements and it provides some basic implementations for
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7 certain methods
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8 """
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9
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10 ## Optional attributes and methods ##
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11
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12 def set_manager(self, manager):
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13 """Set the manager of this component. If this method exists it will be
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14 automatically called when the component is added to a manager.
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15
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16 This method stores the manager and allows the component to be added
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17 only once to a single manager.
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18 """
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19 assert getattr(self, 'manager', None) is None, 'Component cannot be added to multiple managers'
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20 self.manager = manager
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21
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22 def __del__(self):
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23 """Break circrefs to allow faster collection"""
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24 if hasattr(self, 'manager'):
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25 del self.manager
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26
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27 ## Mandatory methods ##
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28
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29 def add(self, entity_id, data=None, **data_kw):
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30 """Add a data entry in the component for the given entity. Additional
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31 data (if any) for the entry can be provided in the data argument or as
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32 keyword arguments. Additional data is optional and if omitted then
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33 suitable defaults will be used. Return an entity data object
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34 for the new entity entry.
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35
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36 The semantics of the data arguments is up to the component.
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37
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38 An entity_id is a unique key, thus multiple separate data entries for
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39 a given entity are not allowed. Components can indivdually decide
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40 what to do if an entity_id is added multiple times to the component.
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41 Potential options include, raising an exception, replacing the
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42 existing data or coalescing it somehow.
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43 """
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44
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45 def remove(self, entity_id):
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46 """Remove the entity data entry from the component. If the
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47 entity is not in the component, raise KeyError
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48 """
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49
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50 def __delitem_(self, entity_id):
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51 """Same as remove()"""
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52
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53 def __len__(self):
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54 """Return the number of entities in the component"""
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55 raise NotImplementedError()
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56
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57 def __iter__(self):
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58 """Return an iterator of entity data objects in this component
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59
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60 No order is defined for these data objects
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61 """
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62 raise NotImplementedError()
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63
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64 def __contains__(self, entity_id):
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65 """Return True if the entity is contained in the component"""
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66 raise NotImplementedError()
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67
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68 def __getitem__(self, entity_id):
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69 """Return the entity data object for the given entity.
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70 The entity data object returned may be mutable, immutable or a
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71 mutable copy of the data at the discretion of the component
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72 """
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73 raise NotImplementedError()
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74
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