Menu
I came across a ternary in some code and I am having trouble understanding the conditional:
str.split(/',\s*'/).map do |match|
match[0] == ?, ?
match : "some string"
end.join
I do understand that I am splitting a string at certain points and converting the total result to an array, and dealing with each element of the array in turn. Beyond that I have no idea what's going on.
739
The ternary operator is used to return a value based on the result of a binary condition. It takes in a binary condition as input, which makes it similar to an 'if-else' control flow block. It also, however, returns a value, behaving similar to a function.
The conditional (ternary) operator is the only JavaScript operator that takes three operands: a condition followed by a question mark ( ? ), then an expression to execute if the condition is truthy followed by a colon ( : ), and finally the expression to execute if the condition is falsy.
Here's a simple decision-making example using if and else: int a = 10, b = 20, c; if (a < b) { c = a; } else { c = b; } printf("%d", c); This example takes more than 10 lines, but that isn't necessary. You can write the above program in just 3 lines of code using a ternary operator.
The conditional operator is also known as a ternary operator. The conditional statements are the decision-making statements which depends upon the output of the expression. It is represented by two symbols, i.e., '?' and ':'.
A (slightly) less confusing way to write this is:
str.split(/',\s*'/).map do |match|
if match[0] == ?,
match
else
"some string"
end
end.join
I think multiline ternary statements are horrible, especially since if blocks can return in Ruby.
Probably the most confusing thing here is the ?, which is a character literal. In Ruby 1.8 this means the ASCII value of the character (in this case 44), in Ruby 1.9 this is just a string (in this case ",").
The reason for using a character literal instead of just "," is that the return value of calling [] on a string changed in Ruby 1.9. In 1.8 it returned the ASCII value of the character at that position, in 1.9 it returns a single-character string. Using ?, here avoids having to worry about the differences in String#[] between Ruby 1.8 & 1.9.
Ultimately the conditional is just checking if the first character in match is ,, and if so it keeps the value the same, else it sets it to "some string".
112
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
