1 Access to persistent data |
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2 -------------------------- |
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3 |
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4 Python-level access to persistent data is provided by the |
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5 :class:`Entity <cubicweb.entity>` class. |
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6 |
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7 An entity class is bound to a schema entity type. Descriptors are added when |
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8 classes are registered in order to initialize the class according to its schema: |
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9 |
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10 * we can access the defined attributes in the schema thanks to the attributes of |
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11 the same name on instances (typed value) |
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12 |
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13 * we can access the defined relations in the schema thanks to the relations of |
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14 the same name on instances (entities instances list) |
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15 |
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16 |
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17 :Formatting and output generation: |
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18 |
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19 * `view(__vid, __registry='views', **kwargs)`, applies the given view to the entity |
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20 (and returns an unicode string) |
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21 |
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22 * `absolute_url(*args, **kwargs)`, returns an absolute URL to access the primary view |
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23 of an entity |
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24 |
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25 * `rest_path()`, returns a relative REST URL to get the entity |
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26 |
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27 * `printable_value(attr, value=_marker, attrtype=None, format='text/html', displaytime=True)`, |
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28 returns a string enabling the display of an attribute value in a given format |
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29 (the value is automatically recovered if necessary) |
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30 |
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31 :Data handling: |
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32 |
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33 * `as_rset()`, converts the entity into an equivalent result set simulating the |
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34 request `Any X WHERE X eid _eid_` |
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35 |
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36 * `complete(skip_bytes=True)`, executes a request that recovers at |
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37 once all the missing attributes of an entity |
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38 |
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39 * `get_value(name)`, returns the value associated to the attribute name given |
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40 in parameter |
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41 |
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42 * `related(rtype, role='subject', limit=None, entities=False)`, |
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43 returns a list of entities related to the current entity by the |
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44 relation given in parameter |
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45 |
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46 * `unrelated(rtype, targettype, role='subject', limit=None)`, |
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47 returns a result set corresponding to the entities not (yet) |
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48 related to the current entity by the relation given in parameter |
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49 and satisfying its constraints |
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50 |
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51 * `set_attributes(**kwargs)`, updates the attributes list with the corresponding |
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52 values given named parameters |
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53 |
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54 * `set_relations(**kwargs)`, add relations to the given object. To |
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55 set a relation where this entity is the object of the relation, |
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56 use `reverse_<relation>` as argument name. Values may be an |
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57 entity, a list of entities, or None (meaning that all relations of |
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58 the given type from or to this object should be deleted). |
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59 |
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60 * `copy_relations(ceid)`, copies the relations of the entities having the eid |
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61 given in the parameters on the current entity |
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62 |
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63 * `delete()` allows to delete the entity |
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64 |
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65 |
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66 The :class:`AnyEntity` class |
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67 ---------------------------- |
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68 |
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69 To provide a specific behavior for each entity, we have to define a class |
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70 inheriting from `cubicweb.entities.AnyEntity`. In general, we define this class |
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71 in `mycube.entities` module (or in a submodule if we want to split code among |
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72 multiple files) so that it will be available on both server and client side. |
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73 |
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74 The class `AnyEntity` is a sub-class of Entity that add methods to it, |
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75 and helps specializing (by further subclassing) the handling of a |
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76 given entity type. |
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77 |
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78 Most methods defined for `AnyEntity`, in addition to `Entity`, add |
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79 support for the `Dublin Core`_ metadata. |
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80 |
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81 .. _`Dublin Core`: http://dublincore.org/ |
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82 |
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83 :Standard meta-data (Dublin Core): |
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84 |
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85 * `dc_title()`, returns a unicode string corresponding to the |
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86 meta-data `Title` (used by default is the first non-meta attribute |
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87 of the entity schema) |
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88 |
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89 * `dc_long_title()`, same as dc_title but can return a more |
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90 detailed title |
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91 |
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92 * `dc_description(format='text/plain')`, returns a unicode string |
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93 corresponding to the meta-data `Description` (looks for a |
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94 description attribute by default) |
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95 |
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96 * `dc_authors()`, returns a unicode string corresponding to the meta-data |
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97 `Authors` (owners by default) |
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98 |
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99 * `dc_creator()`, returns a unicode string corresponding to the |
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100 creator of the entity |
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101 |
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102 * `dc_date(date_format=None)`, returns a unicode string corresponding to |
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103 the meta-data `Date` (update date by default) |
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104 |
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105 * `dc_type(form='')`, returns a string to display the entity type by |
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106 specifying the preferred form (`plural` for a plural form) |
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107 |
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108 * `dc_language()`, returns the language used by the entity |
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109 |
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110 |
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111 :Misc methods: |
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112 |
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113 * `after_deletion_path`, return (path, parameters) which should be |
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114 used as redirect information when this entity is being deleted |
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115 |
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116 * `pre_web_edit`, callback called by the web editcontroller when an |
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117 entity will be created/modified, to let a chance to do some entity |
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118 specific stuff (does nothing by default) |
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119 |
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120 Inheritance |
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121 ----------- |
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122 |
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123 When describing a data model, entities can inherit from other entities as is |
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124 common in object-oriented programming. |
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125 |
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126 You have the possibility to adapt some entity attributes, as follow: |
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127 |
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128 .. sourcecode:: python |
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129 |
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130 from cubes.OTHER_CUBE import entities |
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131 class EntityExample(entities.EntityExample): |
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132 def dc_long_title(self): |
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133 return '%s (%s)' % (self.name, self.description) |
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134 |
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135 Notice this is different than yams schema inheritance. |
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136 |
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