Ruby is pass-by-value, but the values it passes are references.

The variable is not the object, variable is a “box” that point to the object

exmaple: a = []

a is a variable, refer to the array object. it not a array itself. a is “box”, contain the array

Pass-by-reference

the box (the variable) is passed directly into the function refer to the exact same object in memory for variable in function context and for the caller.

=> Pass-by-reference –> reference to exactly memory of object –> varable will be change

Pass-value-by-value

In pass-value-by-value, the function receives a copy of the argument objects passed to it by the caller, stored in a new location in memory.

The copies of variables and objects in the context of the caller are completely isolated. *(variable will not change)

Pass-reference-by-value

Ruby is pass-by-value, but the values it passes are references.

Ruby acts like pass by value for immutable objects, pass by reference for mutable objects is a reasonable answer Immediate values are not passed by reference but are passed by value: nil, true, false, Fixnums, Symbols, and some Floats.