Added Iterable:pick method

libs/iterables/Iterable.lua

@@ -236,4 +236,32 @@ function Iterable:select(...)
 	return rows
 end
 
+--[=[
+@m pick
+@p ... string/function
+@r function
+@d This returns an iterator that, when called, returns the values from each
+encountered object, picked by the provided keys. If a key is a string, the objects
+are indexed with the string. If a key is a function, the function is called with
+the object passed as its first argument.
+]=]
+function Iterable:pick(...)
+	local keys = pack(...)
+	local values = {}
+	local n = keys.n
+	return wrap(function()
+		for obj in self:iter() do
+			for i = 1, n do
+				local k = keys[i]
+				if type(k) == 'function' then
+					values[i] = k(obj)
+				else
+					values[i] = obj[k]
+				end
+			end
+			yield(unpack(values, 1, n))
+		end
+	end)
+end
+
 return Iterable