swift - Computed properties cannot store a value but hold a value, what is hold and how to hold? -

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quote "swift apprentice second edition page 225":

properties(computed) hold values can , set. methods perform work

quote "swift official document":

in addition stored properties, classes, structures, , enumerations can define computed properties, not store value

one says "store", 1 says "hold". bit confused computed properties, computed properties not store value means? means system not assign memory space save value , hold it. what's hold means? can't hold in nowhere, need maybe box hold something, isn't it?

simple example documentation

struct cuboid {     var width = 0.0, height = 0.0, depth = 0.0     var volume: double {         return width * height * depth     } }

volume never stored in memory. whenever getter called result of multiplication returned dynamically math operation in local scope.

the official apple documentation not use term hold @ all.


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