You have a class Person with unknown instance variables. How can you write a method update_var(name, value) that updates any instance variable dynamically using instance_variable_set?
hard📝 Application Q8 of 15
Ruby - Metaprogramming Fundamentals
You have a class Person with unknown instance variables. How can you write a method update_var(name, value) that updates any instance variable dynamically using instance_variable_set?
Adef update_var(name, value)
instance_variable_set("@" + name.to_s, value)
end
Bdef update_var(name, value)
instance_variable_set(name.to_sym, value)
end
Cdef update_var(name, value)
instance_variable_set(:name, value)
end
Ddef update_var(name, value)
instance_variable_set(name, value)
end
Step-by-Step Solution
Solution:
Step 1: Understand instance_variable_set argument format
The method requires the instance variable name with '@' prefix as symbol or string.
Step 2: Build variable name dynamically
Concatenate '@' with the string version of name, then pass as string or symbol. def update_var(name, value)
instance_variable_set("@" + name.to_s, value)
end does this correctly.
Step 3: Check other options
def update_var(name, value)
instance_variable_set(name, value)
end passes name directly without '@'. def update_var(name, value)
instance_variable_set(:name, value)
end uses literal :name symbol, not dynamic. def update_var(name, value)
instance_variable_set(name.to_sym, value)
end converts name to symbol but misses '@'.
Final Answer:
def update_var(name, value)
instance_variable_set("@" + name.to_s, value)
end -> Option A
Quick Check:
Prefix '@' to variable name string before setting [OK]
Quick Trick:Add '@' prefix to variable name string before setting [OK]
Common Mistakes:
Passing variable name without '@'
Using fixed symbol instead of dynamic name
Converting name to symbol without '@'
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