gtk:tree-model-iter-nth-child (model parent n)

model -- a gtk:tree-model object
parent -- a gtk:tree-iter iterator to get the child from, or nil
n -- an integer with the index of the desired child

The gtk:tree-iter iterator to the nth child.

Returns the iterator to the child of parent, using the given index. The first index is 0. If n is too big, or parent has no children, nil is returned. The parent iterator will remain a valid node after this function has been called. As a special case, if parent is nil, then the nth root node is returned.