IntoPropValue errors when migrating to 0.18

[huntc]

Hi there - I'm upgrading my codebase from 0.17.4 to 0.18.0 and discovered errors per the following:

the trait `IntoPropValue>>` is not implemented for `u32`

This occurs given html! expressions where I'm passing values into the attributes. Here's an example using SVG's line element:

<line x1={LEFT_MARGIN_X} y1={TOP_MARGIN_Y} x2={LEFT_MARGIN_X} y2={BOTTOM_MARGIN_Y} class="axis-y-line" />

Is it that I must use an explicit .to_string() for each attribute?

Can you please confirm on how I migrate this change? Thanks.

[mc1098]

Hey 👋

Is it that I must use an explicit .to_string() for each attribute?

Yes, Yew used to call ToString::to_string for you before 0.18.0, which in this case is convenient, however, when passing something like an owned String to a child Component this would cause the String to be cloned when it might only need to be borrowed. So Yew 0.18.0 uses Cows under the hood so that owned Strings can be borrowed and only cloned on write.

If your const/static variables are only being used in the html! macro for setting attributes then you can consider using &'static to avoid the to_string calls.

In your Properties, to avoid needless cloning, you can change the String fields to Cow<'static, str>:

Before:

use yew::prelude::*;

#[derive(Clone, Properties)]
pub struct ModelProps {
    text: String,
}

After:

use std::borrow::Cow;
use yew::prelude::*;

#[derive(Clone, Properties)] 
pub struct ModelProps {
    text: Cow<'static, str>,
}

[huntc]

Thanks so much for replying. That's great info. Cheers.