Ruby: How do I retrieve part of a string?

I want a way to only display a set number of characters from a string/text value.

I want it to work in a way that if my_string.length >开发者_开发技巧 40 then only get first 40 characters from my_string?

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simply sub-string your string:

mystring[0...40]

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You could do:

my_string[0..39]

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my_string.slice!(40..-1)

You can check description for slice! here

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If you are already using the activesupport gem (or if you don't mind adding it as a dependency), then you can also use String#truncate. If your string is longer than the set limit you will see "Your string..."

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Ruby lets you slice a string:

my_string = my_string[0, 40] if (my_string.length > 40)

As Andy H reminded me, this can be shorted to:

my_string = my_string[0, 40]

Here's an example:

str = '1234567890' * 5 #=> "12345678901234567890123456789012345678901234567890"
str[0, 40] #=> "1234567890123456789012345678901234567890"