Hashes

Quick reference

• 00:04 In this video, I want to talk about hashes and hashes are an awful lot like arrays.
• 00:08 In fact, let's go ahead and create an array again.
• 00:12 And let's just do our basic John, Tim, Mary,
• 00:18 Bluto, whatever, and we remember to access this
• 00:24 we need to say puts names and then give it an index number.
• 00:29 So if we want Tim, we would put 1, so if we save this and run it, we get Tim.
• 00:35 The problem with arrays is you have to know the numbers of the things.
• 00:39 So in order to output Tim, I need to know that it's the 1th item in our array.
• 00:44 If I want to print out John, I need to know that it's the 0th item in our array.
• 00:48 And that can be kind of a hassle.
• 00:50 Well, hashes, like I said,
• 00:51 they're very much like arrays only we don't need to know the numbers.
• 00:54 They're not indexed by numbers, they're indexed by keywords.
• 00:57 So to create a hash, start out the same, we name it.
• 01:01 So I'm going to name this favorite_pizza and set it equal to and an array
• 01:06 we use those straight brackets, with a hash we use our curly brackets, right.
• 01:12 So hashes have pairs.
• 01:14 They're called keys and values, and the key is on the left and
• 01:18 the value is on the right.
• 01:19 They're separated by something called a hash rocket.
• 01:21 So to build one of these things we just, let's go,
• 01:23 John, and then here's our hash rocket.
• 01:26 It kind of looks like a little rocket, an arrow pointing that way.
• 01:29 And then we add the value, the thing we want to store.
• 01:31 So my favorite pizza is pepperoni.
• 01:35 Is that how you spell pepperoni?
• 01:36 I have no idea, pepperoni, and like an array, we separate each item with a comma.
• 01:40 You can put all these on the same line like an array but
• 01:43 it quickly becomes very hard to read.
• 01:45 So the convention is to put each item on its own separate line.
• 01:48 So we could go Tim and hash rocket him, Tim likes mushroom and
• 01:55 we've got Mary, Mary likes cheese.
• 02:02 And we've got Bluto and
• 02:05 Bluto likes supreme pizza.
• 02:09 So Bluto is the last guy, so he doesn't need a comma at the end.
• 02:13 So we save this.
• 02:14 Now we've got our hash.
• 02:15 So how do we access a hash?
• 02:17 It's very much like an array.
• 02:19 We go puts, and then call it favorite_pizza.
• 02:22 And then just like an array, we use our brackets.
• 02:25 And now you call the key, so like I said, the key's on the left,
• 02:28 the value is on the right.
• 02:29 So if we call the key of John, it will output John's value,
• 02:33 John's favorite pizza, in this case, pepperoni.
• 02:36 So if we save this, I'll go up here and
• 02:38 hit reload, we're putting out let's comment this guy out.
• 02:42 We save it, hit reload, we get pepperoni.
• 02:45 So if we want to know Mary's favorite pizza,
• 02:48 we just type in Mary and we get cheese.
• 02:51 If we want to know Bluto, just type in Bluto, supreme.
• 02:56 Now the problem with arrays, you have to know which number is the item.
• 03:00 So if we want to know Tim's number, we need to know he's the 1th person.
• 03:04 Hashes you don't need to do that.
• 03:05 You just need to type in Tim and you'll get Tim's value.
• 03:08 Now of course, you still need to know that there's a Tim in there.
• 03:11 But now what do you want?
• 03:13 So those are hashes, very powerful.
• 03:15 You'll use hashes an awful lot.
• 03:17 Sometimes it's a matter of using an array or a hash,
• 03:20 and just depending on the data that you have,
• 03:22 the stuff that goes in it will determine whether you use a hash or an array.
• 03:26 They act very similar.
• 03:27 You can put all kinds of stuff in hashes.
• 03:29 You can put hashes inside of an array, right?
• 03:33 So we put arrays in our arrays, we put strings in our arrays, we put numbers,
• 03:37 variables, you can put hashes.
• 03:39 So in the next video, we'll look at how to manipulate hashes.

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