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OneToOneMapping navigable from both sides - how?

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jtuchel

OneToOneMapping navigable from both sides - how?

I seem to be sitting on some cable, because I can't find a solution to a seemingly easy problem.

What I need is a OneToOne Relationship in which both objects hold their counterpart in an instance variable. Something like married couples. Husbands should know their wife, but wives should also know their husband.

The classes look something like:

Man class iVars: name, birthday, ... and wife

Woman class iVars: name, birthday, ... and husband

here's what the descriptor for the Man Class / Table would look like:

(aDescriptor newMapping: OneToOneMapping)

attributeName: #wife;

referenceClass: Woman;

mappingCriteria: (

Join

from: (table fieldNamed: 'wife_id')

to: ((self tableNamed: 'WOMAN') fieldNamed: 'id'))

Since the model I am working on is a bit more complex, adding a column 'husband_id' to the WOMAN table is not an option I would prefer. I'd like to add a backpointer to the mappings that uses the 'wife_id' column in the MAN table to determine which man to put into the #husband instance variable.

So how can I make this relationship navigable from both sides without adding another id to the WOMAN table? I guess it's not too hard, but you know how it goes..

Joachim

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Maarten Mostert

RE: OneToOneMapping navigable from both sides - how?

Did you think about using a link table ?

> "jtuchel" <[hidden email]> |

I seem to be sitting on some cable, because I can't find a solution to a seemingly easy problem.

The classes look something like:

Man class iVars: name, birthday, ... and wife

Woman class iVars: name, birthday, ... and husband

here's what the descriptor for the Man Class / Table would look like:

(aDescriptor newMapping: OneToOneMapping)

attributeName: #wife;

referenceClass: Woman;

mappingCriteria: (

Join

from: (table fieldNamed: 'wife_id')

to: ((self tableNamed: 'WOMAN') fieldNamed: 'id'))

So how can I make this relationship navigable from both sides without adding another id to the WOMAN table? I guess it's not too hard, but you know how it goes..

Joachim

jtuchel

Re: OneToOneMapping navigable from both sides - how?

Well, no. A link table would make things even more complex, wouldn't it?

Am Mittwoch, 26. Juni 2013 11:48:35 UTC+2 schrieb [hidden email]:

Did you think about using a link table ?

> "jtuchel" <<a href="javascript:" target="_blank" gdf-obfuscated-mailto="OBJOxRxoacsJ">jtu...@...> |

I seem to be sitting on some cable, because I can't find a solution to a seemingly easy problem.

What I need is a OneToOne Relationship in which both objects hold their counterpart in an instance variable. Something like married couples. Husbands should know their wife, but wives should also know their husband.

The classes look something like:

Man class iVars: name, birthday, ... and wife

Woman class iVars: name, birthday, ... and husband

here's what the descriptor for the Man Class / Table would look like:

(aDescriptor newMapping: OneToOneMapping)

attributeName: #wife;

referenceClass: Woman;

mappingCriteria: (

Join

from: (table fieldNamed: 'wife_id')

to: ((self tableNamed: 'WOMAN') fieldNamed: 'id'))

Since the model I am working on is a bit more complex, adding a column 'husband_id' to the WOMAN table is not an option I would prefer. I'd like to add a backpointer to the mappings that uses the 'wife_id' column in the MAN table to determine which man to put into the #husband instance variable.

So how can I make this relationship navigable from both sides without adding another id to the WOMAN table? I guess it's not too hard, but you know how it goes..

Joachim
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Maarten Mostert

Re: OneToOneMapping navigable from both sides - how?

No I think it is pretty straith forward, also there must be quite some examples out there to do so.

Give it a try ..

@+Maarten,

> "jtuchel" <[hidden email]> |

Well, no. A link table would make things even more complex, wouldn't it?

Am Mittwoch, 26. Juni 2013 11:48:35 UTC+2 schrieb [hidden email]:

Did you think about using a link table ?

> "jtuchel" <<a href="javascript:" target="_blank">jtu...@...> |

I seem to be sitting on some cable, because I can't find a solution to a seemingly easy problem.

What I need is a OneToOne Relationship in which both objects hold their counterpart in an instance variable. Something like married couples. Husbands should know their wife, but wives should also know their husband.

The classes look something like:

Man class iVars: name, birthday, ... and wife

Woman class iVars: name, birthday, ... and husband

here's what the descriptor for the Man Class / Table would look like:

(aDescriptor newMapping: OneToOneMapping)

attributeName: #wife;

referenceClass: Woman;

mappingCriteria: (

Join

from: (table fieldNamed: 'wife_id')

to: ((self tableNamed: 'WOMAN') fieldNamed: 'id'))

Since the model I am working on is a bit more complex, adding a column 'husband_id' to the WOMAN table is not an option I would prefer. I'd like to add a backpointer to the mappings that uses the 'wife_id' column in the MAN table to determine which man to put into the #husband instance variable.

So how can I make this relationship navigable from both sides without adding another id to the WOMAN table? I guess it's not too hard, but you know how it goes..

Joachim
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Alan Knight-2

Re: OneToOneMapping navigable from both sides - how?

In reply to this post by jtuchel

That should just work. On the wife side you just have an attribute #husband whose join is from id to wife_id. In fact, in the absence of polygamy, you should be able to leave off the join and let Glorp figure it out. If it knows the class, and there's only one join that would work between the tables those classes are mapped to, it will use it automatically.

On 26 June 2013 00:36, jtuchel <[hidden email]> wrote:

I seem to be sitting on some cable, because I can't find a solution to a seemingly easy problem.

What I need is a OneToOne Relationship in which both objects hold their counterpart in an instance variable. Something like married couples. Husbands should know their wife, but wives should also know their husband.

The classes look something like:
Man class iVars: name, birthday, ... and wife
Woman class iVars: name, birthday, ... and husband

here's what the descriptor for the Man Class / Table would look like:

(aDescriptor newMapping: OneToOneMapping)
attributeName: #wife;
referenceClass: Woman;

mappingCriteria: (
Join
from: (table fieldNamed: 'wife_id')

to: ((self tableNamed: 'WOMAN') fieldNamed: 'id'))

Since the model I am working on is a bit more complex, adding a column 'husband_id' to the WOMAN table is not an option I would prefer. I'd like to add a backpointer to the mappings that uses the 'wife_id' column in the MAN table to determine which man to put into the #husband instance variable.

So how can I make this relationship navigable from both sides without adding another id to the WOMAN table? I guess it's not too hard, but you know how it goes..

Joachim

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Maarten Mostert

Re: OneToOneMapping navigable from both sides - how?

It is a real pain however when husband and wife seperate and go there way with differents partners.

Often the update doesn't get through. At least with a link table you can surpress the mariage refresh partners and rebuild life from there ...

> "Alan Knight" <[hidden email]> |

On 26 June 2013 00:36, jtuchel <[hidden email]> wrote:

I seem to be sitting on some cable, because I can't find a solution to a seemingly easy problem.
What I need is a OneToOne Relationship in which both objects hold their counterpart in an instance variable. Something like married couples. Husbands should know their wife, but wives should also know their husband.

The classes look something like:

Man class iVars: name, birthday, ... and wife

Woman class iVars: name, birthday, ... and husband

here's what the descriptor for the Man Class / Table would look like:

(aDescriptor newMapping: OneToOneMapping)

attributeName: #wife;

referenceClass: Woman;

mappingCriteria: (

Join

from: (table fieldNamed: 'wife_id')

to: ((self tableNamed: 'WOMAN') fieldNamed: 'id'))

Since the model I am working on is a bit more complex, adding a column 'husband_id' to the WOMAN table is not an option I would prefer. I'd like to add a backpointer to the mappings that uses the 'wife_id' column in the MAN table to determine which man to put into the #husband instance variable.

So how can I make this relationship navigable from both sides without adding another id to the WOMAN table? I guess it's not too hard, but you know how it goes..

Joachim
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jtuchel

Re: OneToOneMapping navigable from both sides - how?

In reply to this post by Alan Knight-2

Alan,

I just came back to this issue and found out it simply does work ;-)

I was somewhat irritated by the fact that the foreign key is located in the root table and not in the dependent table (as it normally is in 1:n relationships).

Thanks for answering

Joachim

Am Mittwoch, 26. Juni 2013 16:19:58 UTC+2 schrieb Alan Knight:

That should just work. On the wife side you just have an attribute #husband whose join is from id to wife_id. In fact, in the absence of polygamy, you should be able to leave off the join and let Glorp figure it out. If it knows the class, and there's only one join that would work between the tables those classes are mapped to, it will use it automatically.

On 26 June 2013 00:36, jtuchel <<a href="javascript:" target="_blank" gdf-obfuscated-mailto="jFnYvzLbqsUJ">jtu...@...> wrote:
I seem to be sitting on some cable, because I can't find a solution to a seemingly easy problem.

What I need is a OneToOne Relationship in which both objects hold their counterpart in an instance variable. Something like married couples. Husbands should know their wife, but wives should also know their husband.

The classes look something like:
Man class iVars: name, birthday, ... and wife
Woman class iVars: name, birthday, ... and husband

here's what the descriptor for the Man Class / Table would look like:

(aDescriptor newMapping: OneToOneMapping)
attributeName: #wife;
referenceClass: Woman;

mappingCriteria: (
Join
from: (table fieldNamed: 'wife_id')

to: ((self tableNamed: 'WOMAN') fieldNamed: 'id'))

Since the model I am working on is a bit more complex, adding a column 'husband_id' to the WOMAN table is not an option I would prefer. I'd like to add a backpointer to the mappings that uses the 'wife_id' column in the MAN table to determine which man to put into the #husband instance variable.

So how can I make this relationship navigable from both sides without adding another id to the WOMAN table? I guess it's not too hard, but you know how it goes..

Joachim

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