gistfile1.m

// Definitions
NSDictionary *son = @{ @"firstname" : @"James", @"lastname" : @"Appleseed" };
NSDictionary *daughter = @{ @"firstname" : @"Susan", @"lastname" : @"Appleseed"};
NSArray *children = @[son, daughter];
NSDictionary *father = @{ @"firstname" : @"John", @"lastname" : @"Appleseed" };
NSDictionary *family = @{@"children" : children, @"father" : father};
NSDictionary *pedigree = @{@"family" : family };

// First test
id _family = [pedigree objectForKey:@"family"];
if ([_family isKindOfClass:[NSDictionary class]])
{
    NSDictionary *_family = (NSDictionary *)_family;
    id _children = [_family objectForKey:@"children"];
    
    if ([_children isKindOfClass:[NSArray class]]) {
        NSLog(@"Children is an NSArray");
    } else {
        NSLog(@"Children is not an NSArray");
    }
} else {
    NSLog(@"Family is not an NSDictionary");
}

// Output first test: "Children is not an NSArray"

// Second test
id _family = [pedigree objectForKey:@"family"];
if ([_family isKindOfClass:[NSDictionary class]])
{
    id _children = [_family objectForKey:@"children"];
    
    if ([_children isKindOfClass:[NSArray class]]) {
        NSLog(@"Children is an NSArray");
    } else {
        NSLog(@"Children is not an NSArray");
    }
} else {
    NSLog(@"Family is not an NSDictionary");
}

// Output second test: "Children is an NSArray"