gistfile1.m

#import "OResultOutlineViewController.h"

@implementation OResultOutlineViewController

- (id)init
{
    self = [super init];
    if (self) {
        _data = @[@"0",@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"10",@"11",@"12",@"13",@"14"];
    }
    return self;
}

#pragma mark - NSOutlineViewDelegate
- (NSInteger)outlineView:(NSOutlineView *)outlineView numberOfChildrenOfItem:(id)item
{
    if (!item) {
        item = self.data;
    }
    
    NSUInteger returnValue = 0;
    if ([item isKindOfClass:[NSArray class]]) {
        returnValue = [item count];
    }
    return returnValue;
}

- (BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(id)item
{
    id value = item;

    if (![value isKindOfClass:[NSArray class]] && ![value isKindOfClass:[NSDictionary class]]) {
        return NO;
    }
    return [value count];
}

- (id)outlineView:(NSOutlineView *)outlineView child:(NSInteger)index ofItem:(id)item
{
    if (!item) {
        item = self.data;
    }
    id returnValue = @"";
    if ([item isKindOfClass:[NSArray class]]) {
        returnValue = @"value";//[item objectAtIndex:index];
    }

//    return @{@"index":@(index), @"value":returnValue}; // produces EXC_BAD_ACCESS in outlineView:objectValueForTableColumn:byItem:
    return returnValue;
}

- (id)outlineView:(NSOutlineView *)outlineView objectValueForTableColumn:(NSTableColumn *)tableColumn byItem:(id)item
{
    if ([tableColumn.identifier isEqualToString:@"keyColumn"]) {
        return @"key";
    }
    if ([tableColumn.identifier isEqualToString:@"valueColumn"]) {
        return @"value";
    }

    return @"type";
}

@end