filteredArray = [allRecords filteredArrayUsingPredicate:
        [NSPredicate predicateWithFormat:@"someField == %d",   someFieldFilterValue]];

in ruby:

    all_records.select {|r| r.some_field == some_field_filter_value}

in clojure:

    (filter #(= % some-filter-value) all-records)

in haskell:

    filter (\someField -> x == someFilterValue) allRecords