CODEWITHSUNDEEP
ruby
runcode
runcode

Reputation: 3643

ruby passing value into array using send

I am new to ruby , can someone explain what the second and 3rd line do?

a = [6,7,8]
a.send :[]=,0,2
a[0] + a.[](1) + a.send(:[],2)

First line is assigning an array to the variable a.

I am totally lost on second and third line. hope someone can give some detail explannations.

Thanks!!!

Upvotes: 4

Views: 3349

Answers (3)

halfelf
halfelf

Reputation: 10107

You can try the code in irb and see what happens. send means sending the following messages to an object. This feature is inherited from Smalltalk.

So a.send :[]=,0,2 means send the parameter :[]=,0,2 to a. The parenthesis is omitted. The first parameter :[]= is the method to be called by a. Starting with a : means it is a symbol. []= is the method name. The other parameters of send are treated as the parameter of []=.

As you can see in line 3, a.[](1) is equivalent to a[1] in any C-like languages. And a.[]= 0,2 is a[0]=2.

Upvotes: 2

xdazz
xdazz

Reputation: 160833

.send invokes the method identified by symbol, passing it any arguments specified.

a.send :[]=,0,2

is same as

a.send(:[]=, 0, 2)

Means invoke []= method on the array object with first parameter as 0 and second parameter as 2.

So this is a[0] = 2, set the first element of the array to 2.

After executed a.send :[]=,0,2, a becomes [2, 7, 8].

a.[](1) is same as a[1]

a.send(:[], 2) is same as a.[](2) which is a[2].

So a[0] + a.[](1) + a.send(:[],2) equals a[0] + a[1] + a[2] equals 2 +7 + 8 equals 17.

Upvotes: 14

Salil
Salil

Reputation: 47472

a.send :[]=,0,2 ###same as a[0] = 2

a.[](1) ### same as a[1]

a.send(:[],2) ## same as  a[1]

Upvotes: 3

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