基本的Ruby / Rails语法

Question

I am familiar with Java and C and reasonably comfortable with Ruby but get confused by some of the Ruby syntax at times.

For instance what is the following line supposed to be? I assume we are making a function call protect_from_forgery() ?
But what is the meaning of with: :exception ? I guess :exception is a hash value (eg { :exception => "NullPtr" } ) but what is with: ?

protect_from_forgery with: :exception

Answer 1

There is a far bit of syntactic sugar happening in that line. What I think is tripping you up is the shorthand for hashes and symbols. If you're not familiar with symbols, see here for a good tutorial .

With all the syntactic sugar removed, the line could be written as:

protect_from_forgery({:with => :exception})

Breaking it down, the last argument sent to a method is treated as a hash even without the curly braces. So:

protect_from_forgery({:with => :exception})

Is the same as:

protect_from_forgery(:with => :exception)

When a hash's key is a symbol, the hash and key can be defined by putting the colon at the end of the word instead of the beginning. Eg

protect_from_forgery(:with => :exception)

Is the same as:

protect_from_forgery(with: :exception)

Lastly, the brackets around the arguments of a method are optional in Ruby. So:

protect_from_forgery(with: :exception)

Is the same as:

protect_from_forgery with: :exception

Answer 2

Yes protect_from_forgery is a methods which takes optional hast argument optional hast argument

Here with: is a key which is internally a method and :exception is value which is also a methods

see this method protect_from_forgery