help:rustlings/exercises/standard_library_types/iterators2.rs

pub fn capitalize_first(input: &str) -> String {
    let mut c = input.chars();
    match c.next() {
        None => String::new(),
        Some(first) => first.collect::<String>() + c.as_str(),
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    // Step 1.
    // Tests that verify your `capitalize_first` function implementation
    #[test]
    fn test_success() {
        assert_eq!(capitalize_first("hello"), "Hello");
    }

    #[test]
    fn test_empty() {
        assert_eq!(capitalize_first(""), "");
    }

    // Step 2.
    #[test]
    fn test_iterate_string_vec() {
        let words = vec!["hello", "world"];
        let capitalized_words: Vec<String> = // TODO
        assert_eq!(capitalized_words, ["Hello", "World"]);
    }

    #[test]
    fn test_iterate_into_string() {
        let words = vec!["hello", " ", "world"];
        let capitalized_words = // TODO
        assert_eq!(capitalized_words, "Hello World");
    }
}

What is your question?

1 Like

this function doesn't compile

// iterators2.rs
// In this module, you'll learn some of unique advantages that iterators can offer
// Step 1. Complete the `capitalize_first` function to pass the first two cases
// Step 2. Apply the `capitalize_first` function to a vector of strings, ensuring that it returns a vector of strings as well
// Step 3. Apply the `capitalize_first` function again to a list, but try and ensure it returns a single string
// As always, there are hints if you execute `rustlings hint iterators2`!

// I AM NOT DONE

pub fn capitalize_first(input: &str) -> String {
    let mut c = input.chars();
    match c.next() {
        None => String::new(),
        Some(first) => first.collect::<String>() + c.as_str(),
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    // Step 1.
    // Tests that verify your `capitalize_first` function implementation
    #[test]
    fn test_success() {
        assert_eq!(capitalize_first("hello"), "Hello");
    }

    #[test]
    fn test_empty() {
        assert_eq!(capitalize_first(""), "");
    }

    // Step 2.
    #[test]
    fn test_iterate_string_vec() {
        let words = vec!["hello", "world"];
        let capitalized_words: Vec<String> = // TODO
        assert_eq!(capitalized_words, ["Hello", "World"]);
    }

    #[test]
    fn test_iterate_into_string() {
        let words = vec!["hello", " ", "world"];
        let capitalized_words = // TODO
        assert_eq!(capitalized_words, "Hello World");
    }
}

I want to do this exercise, can you help me fix it? and tell me why to do that

You can't use collect because a character is not an iterator. You can use .to_string() instead.

this is hint:
Type 'hint' to get help
hint
Step 1
You need to call something on first before it can be collected
Currently its type is char. Have a look at the methods that are available on that type:
https://doc.rust-lang.org/std/primitive.char.html

Step 2
First you'll need to turn the Vec into an iterator
Then you'll need to apply your function unto each item in the vector
P.s. Don't forget to collect() at the end!

Step 3.
This is very similar to the previous test. The only real change is that you will need to
alter the type that collect is coerced into. For a bonus you could try doing this with a
turbofish

and i don't find proper solution

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.