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Q&A How can I create and modify a struct over iterations of a loop?

You can use an Option to keep track of the mutable state between iterations. Use as_mut to get a mutable reference to the Option's inner value without consuming the Option. Use unwrap on the muta...

posted 5mo ago by Nisha Jadon‭ · edited 4mo ago by GeraldS‭

Answer

#3: Post edited by

GeraldS‭ · 2024-08-05T20:17:20Z (4 months ago)
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**You can use an Option to keep track of the mutable state between iterations.**
**Use as_mut to get a mutable reference to the Option's inner value without consuming the Option.**
**Use unwrap on the mutable reference to access the inner value.**
_See this code just for reference_
~~`let mut sections: Vec<Section> = Vec::new();~~
let mut current_section: Option<Section> = None;
for line in read_to_string("input.ini").unwrap().lines() {
if line.trim().ends_with("]") {
if let Some(section) = current_section.take() {
sections.push(section);
}
current_section = Some(Section::new(line));
} else {
current_section.as_mut().unwrap().add_entry(line);
}
}
if let Some(section) = current_section {
sections.push(section);
}`

**You can use an Option to keep track of the mutable state between iterations.**
**Use as_mut to get a mutable reference to the Option's inner value without consuming the Option.**
**Use unwrap on the mutable reference to access the inner value.**
_See this code just for reference_
```rust
let mut sections: Vec<Section> = Vec::new();
let mut current_section: Option<Section> = None;
for line in read_to_string("input.ini").unwrap().lines() {
if line.trim().ends_with("]") {
if let Some(section) = current_section.take() {
sections.push(section);
}
current_section = Some(Section::new(line));
} else {
current_section.as_mut().unwrap().add_entry(line);
}
}
if let Some(section) = current_section {
sections.push(section);
}
```

#2: Post edited by

Nisha Jadon‭ · 2024-08-05T07:26:49Z (5 months ago)

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**You can use an Option to keep track of the mutable state between iterations.
~~Use as_mut to get a mutable reference to the Option's inner value without consuming the Option.~~
Use unwrap on the mutable reference to access the inner value.**
~~See this code just for reference,~~
~~_`let mut sections: Vec<Section> = Vec::new();~~
~~let mut current_section: Option<Section> = None;~~
~~for line in read_to_string("input.ini").unwrap().lines() {~~
if line.trim().ends_with("]") {
if let Some(section) = current_section.take() {
sections.push(section);
}
current_section = Some(Section::new(line));
} else {
current_section.as_mut().unwrap().add_entry(line);
}
}
~~if let Some(section) = current_section {~~
sections.push(section);
~~}`_~~

**You can use an Option to keep track of the mutable state between iterations.**
**Use as_mut to get a mutable reference to the Option's inner value without consuming the Option.**
**Use unwrap on the mutable reference to access the inner value.**
_See this code just for reference_
`let mut sections: Vec<Section> = Vec::new();
let mut current_section: Option<Section> = None;
for line in read_to_string("input.ini").unwrap().lines() {
if line.trim().ends_with("]") {
if let Some(section) = current_section.take() {
sections.push(section);
}
current_section = Some(Section::new(line));
} else {
current_section.as_mut().unwrap().add_entry(line);
}
}
if let Some(section) = current_section {
sections.push(section);
}`

#1: Initial revision by

Nisha Jadon‭ · 2024-08-05T07:24:37Z (5 months ago)

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**You can use an Option to keep track of the mutable state between iterations.

Use as_mut to get a mutable reference to the Option's inner value without consuming the Option.

Use unwrap on the mutable reference to access the inner value.**

See this code just for reference, 

_`let mut sections: Vec<Section> = Vec::new();
let mut current_section: Option<Section> = None;

for line in read_to_string("input.ini").unwrap().lines() {
    if line.trim().ends_with("]") {
        if let Some(section) = current_section.take() {
            sections.push(section);
        }
        current_section = Some(Section::new(line));
    } else {
        current_section.as_mut().unwrap().add_entry(line);
    }
}

if let Some(section) = current_section {
    sections.push(section);
}`_

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