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Ruby

Posted by deletedaccount
deletedaccount
5,089 Points

Syntax for Ruby method arguments (solved)

I was under the impression that when passing arguments into a method, the brackets can be omitted. So BankAccount.new("Jason") and BankAccount.new "Jason" are interchangeable.

However, when trying out the program in this video, I seem to have found an exception to this rule.

This causes a syntax error:

@transactions.push { amount: amount, memo: options[:memo] }

But this works:

@transactions.push({ amount: amount, memo: options[:memo] })

Anyone care to explain?

1 Answer

Tommy Morgan
STAFF
Tommy Morgan
Treehouse Guest Teacher
Tommy Morgan
Tommy Morgan
Treehouse Guest Teacher

Hi Charles Manfre -

The rule you cite is generally true; there are however two exceptions. The first exception (and the most common) is that the arguments you're providing are ambiguous in some fashion. For example, consider the following:

method1 arg1, method2 arg2, arg3

This could be interpreted in two different ways:

method1(arg1, method2(arg2, arg3))

or

method1(arg1, method2(arg2), arg3)

...so the compiler will complain.

The second exception (and the one you're experiencing) has to do with the fact that the {} syntax in Ruby can mean one of two things: it can represent a hash or it can represent a block, like so:

my_hash = { test: :foo, bar: :baz }

vs.

my_list.map { |list_item| list_item.do_stuff }

When the {} syntax is used in a function call outside of the parentheses, Ruby assumes that you're passing a block to the function and tries to interpret it as such, which leads to the syntax error.

Hope that helps!