CODEWITHSUNDEEP
groovy
Anonymous Human
Anonymous Human

Reputation: 1948

Grails check list for value in map

Is there an easy syntax or convenience method (without looping by myself) for checking to see if a value exists in a Map which is in a List? For example what I am trying to do is:

​def myList = []
myList.push([first: "John", last: "Doe"])
println myList.contains(it -> it.first == "John")

should print true but syntax is incorrect. Basically, I need to know if the list contains a map such that in that map the value of the "first" key is "John".

Upvotes: 2

Views: 1659

Answers (2)

dmahapatro
dmahapatro

Reputation: 50245

Another simpler check could be using spread operator as below

assert 'John' in myList*.first

UPDATE
Benchmarking the performance between usage of find and in provides result that incline towards usage of in if list size is small.

Refer and run this GIST. Results may vary, but it is surprising that in consumes less CPU consistently against find when the list size is small (as shown in question, refer first result). Below is the set of results recorded as I write this update.

                                              user  system      cpu     real

findTestWithSmallerListSize                    571       0      571      598
inListTestWithSmallerListSize                  411       0      411      411

findTestWithMatchPresentInEnd              2714872      43  2714915  2739768
inListTestWithMatchPresentInEnd            2266303      39  2266342  2431595

findTestWithMatchPresentInAverageCenter    2141836      39  2141875  2263714
inListTestWithMatchPresentInAverageCenter  2261387      37  2261424  2438485

findTestWithMatchPresentInFirst            1667364      27  1667391  1813254
inListTestWithMatchPresentInFirst          2288471      37  2288508  2425089

Based on the above result I agree that if the match is present in the beginning or towards the beginning of the list (4th result from above) then find is fully efficient.

Upvotes: 4

Joshua Moore
Joshua Moore

Reputation: 24776

Using find may be a better solution:

def myList = [] 
myList.push([first: "John", last: "Doe"])

def exists = (myList.find{ it -> it.first == 'John'}​​​​​ ? true : false)

assert exists == true

exists = ​(myList.find{ it -> it.first == 'Jane'} ? true : false)

assert exists == false​

Upvotes: 3

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