Can someone please explain the meaning of (!) In Ruby

Question

I've been looking on the internet for ages and I just can't seem to find a place that explains what the (!) symbol means and does......

Answer 1

Its the negation of a logic sentence

Answer 2

An exclamation point refers to NOT something, such as 'not equal' or 'not greater', for example (a > 5), means that a is greater than 5, but with an exclamation point (a !> 5) means a is NOT greater than 5.

Answer 3

there's also another use, when it appears after a method. It basically means that you can call a method inside a variable and automatically store the return value inside the same variable..... Maybe it's easier to understand with some code:

text = "hello" # Store a string inside the text variable
#=>"hello"

text.upcase # Call method upcase to variable text
#=>"HELLO"

text # Call the text variable again, it's value is still in lowercase
#=>"hello"

text.upcase! # This time, call the method and store the return value inside the text variable
#=>"HELLO"

text # Now, the value of text is in uppercase, without having to explicity reassign its value
#=>"HELLO"

Answer 4

A simpler way to explain this is:

text = text.upcase

is the same as

text.upcase!