1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
% Tuple Structs
Rust has another data type that's like a hybrid between a [tuple][tuple] and a
[struct][struct], called a ‘tuple struct’. Tuple structs have a name, but
their fields don’t:
```rust
struct Color(i32, i32, i32);
struct Point(i32, i32, i32);
```
[tuple]: primitive-types.html#tuples
[struct]: structs.html
These two will not be equal, even if they have the same values:
```rust
# struct Color(i32, i32, i32);
# struct Point(i32, i32, i32);
let black = Color(0, 0, 0);
let origin = Point(0, 0, 0);
```
It is almost always better to use a struct than a tuple struct. We would write
`Color` and `Point` like this instead:
```rust
struct Color {
red: i32,
blue: i32,
green: i32,
}
struct Point {
x: i32,
y: i32,
z: i32,
}
```
Now, we have actual names, rather than positions. Good names are important,
and with a struct, we have actual names.
There _is_ one case when a tuple struct is very useful, though, and that’s a
tuple struct with only one element. We call this the ‘newtype’ pattern, because
it allows you to create a new type, distinct from that of its contained value
and expressing its own semantic meaning:
```rust
struct Inches(i32);
let length = Inches(10);
let Inches(integer_length) = length;
println!("length is {} inches", integer_length);
```
As you can see here, you can extract the inner integer type through a
destructuring `let`, as we discussed previously in ‘tuples’. In this case, the
`let Inches(integer_length)` assigns `10` to `integer_length`.
|
