Hash doesn't appear to have a "safe" way to insert an entry that won't clobber another key if it is already there. So how about:
class Hash # Like Hash#store but only stores if the key isn't already # in the hash. Returns true if inserted, otherwise false. # def insert(name, value) if key?(name) false else store(name,value) true end end end
Updated by matz (Yukihiro Matsumoto) about 5 years ago
- Status changed from Open to Feedback
- I am not sure #insert is the best name for non clobbering merge.
do you know merge takes a block to resolve key conflict?
works as your proposed #insert.
Updated by atlas (Atlas Prime) about 5 years ago
The name "insert" seems good to me because it implies a new entry and unable to change an old entry. But key-value pair must be thought of as an entry too for it to make sense (I guess I get that notion from Java http://docs.oracle.com/javase/7/docs/api/java/util/Map.Entry.html).
I did not know that merge took this block. That could be useful. But it's not quite the same because insert returns true/false if successful of not. It's utility is mostly as a short cut for
if !h.key?(k) store(k,v) ... end
Instead one can do
if h.insert(k,v) ... end
However, you make me think it might be useful too if it could take a hash and a block.
def insert_merge(other, &block) other.each do |k, v| if key?(k) block.call(false, k, v) else store(k,v) block.call(true, k, v) end end end