I want to be able to access NSDictionary objects using a key path syntax...

23/07/03 18:56
How to access (set and get) dictionary objects using a key path syntax like @"a.b.c." ?
NSKeyValueCoding protocol.
However, it has some limitations: there is no syntax support for arrays and the "set" (takeValueForKey) functionality requires the complete path to the latest element exist: it will not create intermediary dictionaries for you...
@implementation NSDictionary(GetObjectForKeyPath)

// syntax of path similar to Java: record.array[N].item
// items are separated by . and array indices in []
// example: a.b[N][M].c.d

- (id)objectForKeyPath:(NSString *)inKeyPath
{
NSArray *components = [inKeyPath componentsSeparatedByString:@"."] ;
int i, j, n = [components count], m ;
id curContainer = self ;

for (i=0; i NSString *curPathItem = [components objectAtIndex:i] ;
NSArray *indices = [curPathItem componentsSeparatedByString:@"["] ;

m = [indices count] ;
if (m == 1) { // no [ -> object is a dict or a leave
curContainer = [curContainer objectForKey:curPathItem] ;
}
else {
// indices is an array of string "arrayKeyName" "i1]" "i2]" "i3]"
// arrayKeyName equal to curPathItem

if (![curContainer isKindOfClass:[NSDictionary class]])
return nil ;

curPathItem = [curPathItem substringToIndex:[curPathItem rangeOfString:@"["].location] ;
curContainer = [curContainer objectForKey:curPathItem] ;

for(j=1;j int index = [[indices objectAtIndex:j] intValue] ;

if (![curContainer isKindOfClass:[NSArray class]])
return nil ;

if (index >= [curContainer count])
return nil ;

curContainer = [curContainer objectAtIndex:index];
}
}

}

return curContainer ;
}

-(void)setObject:(id)inValue forKeyPath:(NSString *)inKeyPath
{
NSArray *components = [inKeyPath componentsSeparatedByString:@"."] ;
int i, j, n = [components count], m ;
id containerContainer = nil ;
id curContainer = self ;
NSString *curPathItem = nil ;
NSArray *indices ;
int index ;
BOOL needArray = NO ;

for (i=0; i
curPathItem = [components objectAtIndex:i] ;
indices = [curPathItem componentsSeparatedByString:@"["] ;
m = [indices count] ;


if (m == 1) {
if ([curContainer isKindOfClass:[NSNull class]]) {
curContainer = [NSMutableDictionary dictionary] ;
if (needArray) {
[containerContainer replaceObjectAtIndex:index withObject:curContainer] ;
}
else {
[containerContainer setObject:curContainer forKey:curPathItem] ;
}
}

containerContainer = curContainer ;
curContainer = [curContainer objectForKey:curPathItem] ;

needArray = NO ;
if (![containerContainer isKindOfClass:[NSDictionary class]])
[NSException raise:@"Path item not a dictionary" format:@"(keyPath %@ - offending %@)",inKeyPath,curPathItem] ;

if (curContainer == nil) {
curContainer = [NSMutableDictionary dictionary] ;
[containerContainer setObject:curContainer forKey:curPathItem] ;
}
}
else {
needArray = YES ;
// indices is an array of string "arrayKeyName" "i1]" "i2]" "i3]"
// arrayKeyName equal to curPathItem
curPathItem = [curPathItem substringToIndex:[curPathItem rangeOfString:@"["].location] ;
containerContainer = curContainer ;
curContainer = [curContainer objectForKey:curPathItem] ;

if (curContainer == nil) {
curContainer = [NSMutableArray array] ;
[containerContainer setObject:curContainer forKey:curPathItem] ;
}

if (![curContainer isKindOfClass:[NSArray class]])
[NSException raise:@"Path item not an array" format:@"(keyPath %@ - offending %@)",inKeyPath,curPathItem] ;

for(j=1;j index = [[indices objectAtIndex:j] intValue] ;

containerContainer = curContainer ;
curContainer = [curContainer objectAtIndex:index] ;
if ([curContainer isKindOfClass:[NSNull class]]) {
curContainer = [NSMutableArray array] ;
[containerContainer replaceObjectAtIndex:index withObject:curContainer] ;
}
else if (![curContainer isKindOfClass:[NSArray class]])
[NSException raise:@"Path item not an array" format:@"(keyPath %@ - offending %@ index %d)",inKeyPath,curPathItem,j-1] ;
}

index = [[indices objectAtIndex:m-1] intValue] ;

if (index >= [curContainer count]) {
int k ;

for (k=[curContainer count]; k<=index; k++)
[curContainer addObject:[NSNull null]] ;
}

containerContainer = curContainer ;
curContainer = [curContainer objectAtIndex:index] ;
}

}

if (needArray) { // containerContainer must be an array
if (![containerContainer isKindOfClass:[NSArray class]])
[NSException raise:@"Last path item is not an array" format:@"(keyPath %@)",inKeyPath] ;
[containerContainer replaceObjectAtIndex:index withObject:inValue] ;
}
else {
if (![containerContainer isKindOfClass:[NSDictionary class]])
[NSException raise:@"Before-last path item is not a dictionary" format:@"(keyPath %@)",inKeyPath] ;

[containerContainer setObject:inValue forKey:curPathItem] ;
}
}

@end
First solution: