Diversion: Double-Quoted Strings

So far, we’ve used only single-quoted strings. They are the easiest to use, in the same sense that a shovel is easier to use than a backhoe: when the job gets big enough, it stops being easier.

Consider multiline strings:

Using double quotes, we can indent the strings so they all line up. You’ll notice the “ ”, which is the escape sequence for the newline character. With this, you can also put a multiline string on one line of code:

But it doesn’t work with the simpler single-quoted strings:

And just as you must escape single quotes in single-quoted strings (but not double quotes), you must escape double quotes in double-quoted strings (but not single quotes):

So, that’s double-quoted strings. In most cases, I prefer the simplicity of single-quoted strings, honestly. But there’s one thing that double-quoted strings do very nicely: interpolation. It’s sort of a cross between string addition, to_s conversion, and salsa. (The food or the dance—pick whichever metaphor works best for you.)

Snazzy, no? We got to use the variable names right in the string, just by putting it inside “#{...}”. And you’ll notice that we didn’t have to say zip.to_s to convert the ZIP code to a string; Ruby knows that you want it to be a string in this case, so it does the conversion for you.

But it gets even better! You’re not limited to variables when using string interpolation—you can use any expression you want! Ruby evaluates the expression for you, converts to string, and injects the result into the surrounding string:

Good stuff. (Don’t say I never gave you nothing.)