1 """

     2 28. Many-to-many relationships between the same two tables

     3 

     4 In this example, A Person can have many friends, who are also people. Friendship is a

     5 symmetrical relationship - if I am your friend, you are my friend.

     6 

     7 A person can also have many idols - but while I may idolize you, you may not think

     8 the same of me. 'Idols' is an example of a non-symmetrical m2m field. Only recursive

     9 m2m fields may be non-symmetrical, and they are symmetrical by default.

    10 

    11 This test validates that the m2m table will create a mangled name for the m2m table if

    12 there will be a clash, and tests that symmetry is preserved where appropriate.

    13 """

    14 

    15 from django.db import models

    16 

    17 class Person(models.Model):

    18     name = models.CharField(maxlength=20)

    19     friends = models.ManyToManyField('self')

    20     idols = models.ManyToManyField('self', symmetrical=False, related_name='stalkers')

    21 

    22     def __str__(self):

    23         return self.name

    24 

    25 __test__ = {'API_TESTS':"""

    26 >>> a = Person(name='Anne')

    27 >>> a.save()

    28 >>> b = Person(name='Bill')

    29 >>> b.save()

    30 >>> c = Person(name='Chuck')

    31 >>> c.save()

    32 >>> d = Person(name='David')

    33 >>> d.save()

    34 

    35 # Add some friends in the direction of field definition

    36 # Anne is friends with Bill and Chuck

    37 >>> a.friends.add(b,c)

    38 

    39 # David is friends with Anne and Chuck - add in reverse direction

    40 >>> d.friends.add(a,c)

    41 

    42 # Who is friends with Anne?

    43 >>> a.friends.all()

    44 [<Person: Bill>, <Person: Chuck>, <Person: David>]

    45 

    46 # Who is friends with Bill?

    47 >>> b.friends.all()

    48 [<Person: Anne>]

    49 

    50 # Who is friends with Chuck?

    51 >>> c.friends.all()

    52 [<Person: Anne>, <Person: David>]

    53 

    54 # Who is friends with David?

    55 >>> d.friends.all()

    56 [<Person: Anne>, <Person: Chuck>]

    57 

    58 # Bill is already friends with Anne - add Anne again, but in the reverse direction

    59 >>> b.friends.add(a)

    60 

    61 # Who is friends with Anne?

    62 >>> a.friends.all()

    63 [<Person: Bill>, <Person: Chuck>, <Person: David>]

    64 

    65 # Who is friends with Bill?

    66 >>> b.friends.all()

    67 [<Person: Anne>]

    68 

    69 # Remove Anne from Bill's friends

    70 >>> b.friends.remove(a)

    71 

    72 # Who is friends with Anne?

    73 >>> a.friends.all()

    74 [<Person: Chuck>, <Person: David>]

    75 

    76 # Who is friends with Bill?

    77 >>> b.friends.all()

    78 []

    79 

    80 # Clear Anne's group of friends

    81 >>> a.friends.clear()

    82 

    83 # Who is friends with Anne?

    84 >>> a.friends.all()

    85 []

    86 

    87 # Reverse relationships should also be gone

    88 # Who is friends with Chuck?

    89 >>> c.friends.all()

    90 [<Person: David>]

    91 

    92 # Who is friends with David?

    93 >>> d.friends.all()

    94 [<Person: Chuck>]

    95 

    96 

    97 # Add some idols in the direction of field definition

    98 # Anne idolizes Bill and Chuck

    99 >>> a.idols.add(b,c)

   100 

   101 # Bill idolizes Anne right back

   102 >>> b.idols.add(a)

   103 

   104 # David is idolized by Anne and Chuck - add in reverse direction

   105 >>> d.stalkers.add(a,c)

   106 

   107 # Who are Anne's idols?

   108 >>> a.idols.all()

   109 [<Person: Bill>, <Person: Chuck>, <Person: David>]

   110 

   111 # Who is stalking Anne?

   112 >>> a.stalkers.all()

   113 [<Person: Bill>]

   114 

   115 # Who are Bill's idols?

   116 >>> b.idols.all()

   117 [<Person: Anne>]

   118 

   119 # Who is stalking Bill?

   120 >>> b.stalkers.all()

   121 [<Person: Anne>]

   122 

   123 # Who are Chuck's idols?

   124 >>> c.idols.all()

   125 [<Person: David>]

   126 

   127 # Who is stalking Chuck?

   128 >>> c.stalkers.all()

   129 [<Person: Anne>]

   130 

   131 # Who are David's idols?

   132 >>> d.idols.all()

   133 []

   134 

   135 # Who is stalking David

   136 >>> d.stalkers.all()

   137 [<Person: Anne>, <Person: Chuck>]

   138 

   139 # Bill is already being stalked by Anne - add Anne again, but in the reverse direction

   140 >>> b.stalkers.add(a)

   141 

   142 # Who are Anne's idols?

   143 >>> a.idols.all()

   144 [<Person: Bill>, <Person: Chuck>, <Person: David>]

   145 

   146 # Who is stalking Anne?

   147 [<Person: Bill>]

   148 

   149 # Who are Bill's idols

   150 >>> b.idols.all()

   151 [<Person: Anne>]

   152 

   153 # Who is stalking Bill?

   154 >>> b.stalkers.all()

   155 [<Person: Anne>]

   156 

   157 # Remove Anne from Bill's list of stalkers

   158 >>> b.stalkers.remove(a)

   159 

   160 # Who are Anne's idols?

   161 >>> a.idols.all()

   162 [<Person: Chuck>, <Person: David>]

   163 

   164 # Who is stalking Anne?

   165 >>> a.stalkers.all()

   166 [<Person: Bill>]

   167 

   168 # Who are Bill's idols?

   169 >>> b.idols.all()

   170 [<Person: Anne>]

   171 

   172 # Who is stalking Bill?

   173 >>> b.stalkers.all()

   174 []

   175 

   176 # Clear Anne's group of idols

   177 >>> a.idols.clear()

   178 

   179 # Who are Anne's idols

   180 >>> a.idols.all()

   181 []

   182 

   183 # Reverse relationships should also be gone

   184 # Who is stalking Chuck?

   185 >>> c.stalkers.all()

   186 []

   187 

   188 # Who is friends with David?

   189 >>> d.stalkers.all()

   190 [<Person: Chuck>]

   191 

   192 """}