Arg does not live long enough, for pushing a string to vec

[leyloe]

bad code i know, but why is it saying:

arg does not live long enough borrowed value does not live long enough main.rs(59, 5): arg dropped here while still borrowed main.rs(56, 13): binding arg declared here main.rs(42, 9): borrow later stored here

im so confused

let args = if params.feature.any_feature() {
        let mut features = Vec::new();
        if params.feature.feature0 {
            features.push("feature0")
        }
        if params.feature.feature1 {
            features.push("feature1")
        }
        if params.feature.feature2 {
            features.push("feature2")
        }
        if params.feature.feature3 {
            features.push("feature3")
        }
        let arg = features.join(",");

        vec!["build", "--release", "--features", &arg]
    } else {
        vec!["build", "--release"]
    };

[quinedot]

You can't store a reference to a variable for longer than the variable exists:

    let args = if true {
        let mut features = Vec::<&str>::new();
        let arg = features.join(",");
        vec!["build", "--release", "--features", &arg]
        // Here at the end of the block, `arg` goes out of scope
        // and gets destructed (the `String` gets deallocated).
        // That's not compatible with `&arg` being in `args`, which
        // lasts beyond this block.
    } else {
        vec!["build", "--release"]
    };

There's ways to make this work with args: Vec<&str> within a single function body, but your best bet is probably going to be to use a Vec<String> instead of a Vec<&str>. Then the args will own the data and you don't have to worry about the lifetime problems.

    let args = if true {
        let mut features = Vec::<&str>::new();
        let arg = features.join(",");
        vec![
            "build".to_string(),
            "--release".to_string(),
            "--features".to_string(),
            arg,
        ]
    } else {
        vec!["build".to_string(), "--release".to_string()]
    };