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836134202e
The existing test can be solved with the following:
```rs
while let Some(integer) = optional_integers.pop() {
assert_eq!(integer.unwrap(), range);
```
Similarly with `expect(...)`, `unwrap_or(0)`, `unwrap_or_default()`, etc. However, none of these solutions use the learning point of stacking `Option<T>`s.
The updated test can _only_ be solved by stacking `Option<T>`s:
```rs
while let Some(Some(integer)) = optional_integers.pop() {
assert_eq!(integer, cursor);
```
With the updated test, using `unwrap` or `expect` will panic when it hits the `None` value, and using `unwrap_or` or `unwrap_or_default` will cause the final `assert_eq!(cursor, 0)` to panic.
39 lines
1,009 B
Rust
39 lines
1,009 B
Rust
// options2.rs
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// Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.
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// I AM NOT DONE
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#[cfg(test)]
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mod tests {
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#[test]
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fn simple_option() {
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let target = "rustlings";
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let optional_target = Some(target);
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// TODO: Make this an if let statement whose value is "Some" type
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word = optional_target {
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assert_eq!(word, target);
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}
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}
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#[test]
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fn layered_option() {
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let range = 10;
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let mut optional_integers: Vec<Option<i8>> = vec![None];
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for i in 1..(range + 1) {
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optional_integers.push(Some(i));
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}
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let mut cursor = range;
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// TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
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// You can stack `Option<T>`s into while let and if let
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integer = optional_integers.pop() {
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assert_eq!(integer, cursor);
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cursor -= 1;
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}
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assert_eq!(cursor, 0);
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}
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}
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