i have array ["moniker", @moniker] moniker can 1 of around 100 instance variables , string representation. want change instance variable located @ index 1 referencing (not data itself, may immutable). doing array[1] = newdata doesn't work because changes whats in array. know simple in c, i'm struggling find way in ruby.
your struggle because thinking c programmer, have access underlying pointers, , mutable. in c, array store pointer mutable integer, , change integer whenever want. in ruby, every variable reference object, and numbers immutable objects. so, @moniker reference object, integer 4. when create array, copy reference array, integer 4 has 2 references: 1 @moniker, , 1 array. have found, changing reference in array not change reference named @moniker--it still refers object 4.
"box" reference in array
this not ruby way of doing things. i'm showing because might illustrate how ruby works references.
you can box reference in array:
@moniker = [4] = ["moniker", @moniker] this requires deference array when want access underlying object:
@moniker.first a[1].first but can change underlying integer in @moniker , array see change:
@moniker[0] = 42 p a[1].first # => 42 encapsulate number in mutable object.
being object oriented language, might encapsulate number in mutable object.
class moniker attr_accessor :value def initialize(value) @value = value end end (attr_accessor :value builds reader , writer methods instance variable @value).
@moniker = moniker.new(4) = ["monikier", @moniker] @moniker.value = 42 p a[1].value # => 42 you chose better name "value." couldn't because don't know value represents.
why these 2 solutions work
this comment jörg w mittag, deserves part of answer:
it may seem obvious, wanted mention explicitly: 2 solutions same solution. first uses existing class generic semantics, the second defines new class precise semantics specific encapsulated value. in both cases, it's wrapping immutable value in mutable value , mutating "outer" value.
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