person = % {
first_name: "Jon" ,
last_name: "Snow" ,
age: 27
} Maps represent structured data, like a person assert person == % { first_name: ___ , last_name: "Snow" , age: 27 } Fetching a value returns a tuple with ok when it exists assert Map . fetch ( person , :age ) == ___ Or the atom :error when it doesn't assert Map . fetch ( person , :family ) == ___ Extending a map is as simple as adding a new pair person_with_hobby = Map . put ( person , :hobby , "Kayaking" ) assert Map . fetch ( person_with_hobby , :hobby ) == ___ Put can also overwrite existing values older_person = Map . put ( person , :age , 37 ) assert Map . fetch ( older_person , :age ) == ___ Or you can use some syntactic sugar for existing elements younger_person = % { person | age: 16 } assert Map . fetch ( younger_person , :age ) == ___ without_age = Map . delete ( person , :age ) assert Map . has_key? ( without_age , :age ) == ___ assert Map . merge ( % { first_name: "Jon" } , % { last_name: "Snow" } ) == ___ When merging, the last map wins merged = Map . merge ( person , % { last_name: "Baratheon" } ) assert Map . fetch ( merged , :last_name ) == ___ You can also select sub-maps out of a larger map assert Map . take ( person , [ :first_name , :last_name ] ) == ___