57 lines
1.7 KiB
Rust
57 lines
1.7 KiB
Rust
use bad_optics::prelude::*;
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#[macro_use]
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extern crate bad_optics;
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// the Optics derive macro will implement lenses for every public field in the struct
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// it makes a module named whatever the struct is called, but in lower case
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// you can rename the generated module by adding `#[mod_name = "other_name"]` to the struct
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#[derive(Optics, Clone, Debug)]
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pub struct MyStruct {
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pub field1: String,
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pub field2: String,
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pub field3: u8,
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_field4: u8,
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}
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fn main() {
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let o = MyStruct {
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field1: "first field".to_string(),
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field2: "second field".to_string(),
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field3: 12,
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_field4: 1,
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};
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// we can manually get lenses for each field
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// note that it's a function that returns a lens
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//
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// these lenses work for `MyStruct` with `view` and `over`,
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// and for `&MyStruct` with `view`
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let field1 = <MyStruct as HasLens>::Lenses::field1();
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// short macro for convenience, expands to the line above
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let field2 = lens!(MyStruct::field2);
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// the lenses work normally as any other lens :)
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assert_eq!(field1(&o), "first field");
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assert_eq!(field2(&o), "second field");
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// we can get a vec with all the lenses that match a type
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let string_lenses = <MyStruct as HasLensOf<String>>::get();
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assert_eq!(string_lenses.len(), 2);
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// since _field4 is private, there's no lens for it
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let u8_lenses = <MyStruct as HasLensOf<u8>>::get();
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assert_eq!(u8_lenses.len(), 1);
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// short macro for convenience, expands to the line above
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let _u8_lenses = lenses!(MyStruct::u8);
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let mut o = o;
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for lens in string_lenses {
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o = lens(o, |s| s.to_ascii_uppercase());
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}
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dbg!(o);
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}
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