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POdisplaying a to-many relationship in a view (NSTableColumn) via Binding and Value Transformer
 

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  1. POdisplaying a to-many relationship in a view (NSTableColumn) via Binding and Value Transformer
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    <p>I have an entity Tag (in core data) that have some attributes and a to-many relationship named "aliases".</p> <p>My ArrayController is "bind" in Xcode to:</p> <pre><code>Parameters-&gt;Managed Object Context = File's Owner.managedObjectContext </code></pre> <p>It work OK for all Attributes, the others columns present the correct values.</p> <p>In one column I try to "display" this to-many relationship. If I do it naively and bind the Value of my NSTableColumn to my ArrayController.arrangedObjects.aliases (like all other attributes) I get this on the screen:</p> <blockquote> <p>Relationship fault for (), name aliases, isOptional 1, isTransient 0, entity Tag, renamingIdentifier aliases, validation predicates ( ), warnings ( ), versionHashModifier (null), destination entity TagAlias, inverseRelationship tag, minCount 0, maxCount 0 on 0x10053db10</p> </blockquote> <p>It seems to be some kind of CoreData proxy for the relationship...</p> <p>I then build a subclass of NSValueTransformer:</p> <pre><code>@interface tagAliasesToStringTransformer : NSValueTransformer + (Class)transformedValueClass; + (BOOL)allowsReverseTransformation; - (id)transformedValue:(id)value; @end </code></pre> <p>and tried to use it as a Value Transformer in the binding. But I'm lost in my implementation:</p> <pre><code>@implementation tagAliasesToStringTransformer + (Class)transformedValueClass { return [NSString class]; } + (BOOL)allowsReverseTransformation { return NO; } - (id)transformedValue:(id)value { if (value == nil) return nil; ... } @end </code></pre> <p>In the method transformedValue:, value is of class '_NSFaultingMutableSet' and I don't know how to get a Set/Array of the aliases or anything useful.</p> <p>The goal is to build a NSString of the concatenation of each alias. Something like:</p> <blockquote> <p>aTag : alias1 alias2 alias3 ...</p> </blockquote>
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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