Collection Operators-An introduction.

Objective:
                 To get an understanding of collection operators and to use it effectively.

What is an collection operator?
                                                  Collection operators are specialised key-paths that are passed as the parameter to the valueforkeypath: method .The operator is preceded by (@),some of the collection operators -@avg,@max,@min,@count,@sum;

Example:
               To find the avg of the objects in an array.

Approach-1:
               
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