Question

I have the following map:

def map = [];
map.add([ item: "Shampoo", count: 5 ])
map.add([ item: "Soap", count: 3 ])

I would like to get the sum of all the count properties in the map. In C# using LINQ, it would be something like:

map.Sum(x => x.count)

How do I do the same in Groovy?

Answer 1

Assuming you have a list like so:

List list = [ [item: "foo", count: 5],
              [item: "bar", count: 3] ]

Then there are multiple ways of doing it. The most readable is probably

int a = list.count.sum()

Or you could use the Closure form of sum on the whole list

int b = list.sum { it.count }

Or you could even use a more complex route such as inject

int c = list.count.inject { tot, ele -> tot + ele } // Groovy 2.0
//  c = list.count.inject( 0 ) { tot, ele -> tot + ele } // Groovy < 2.0

All of these give the same result.

assert ( a == b ) && ( b == c ) && ( c == 8 )

I would use the first one.