Flip 293: Stringer interface #294
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[Just cross-referencing] There were some concerns raised before, over having a user-defined |
8 tasks
turbolent
approved these changes
Oct 22, 2024
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| ## Objective | ||
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| This flip proposes the addition of a struct interface `StructStringer` which all string-convertible structs will implement. One goal of this FLIP is to simplify the process for representing `AnyStruct` as a `String`. Secondly, a customizable `toString` will be useful for future string formatting such as string interpolation with this interface. |
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| This flip proposes the addition of a struct interface `StructStringer` which all string-convertible structs will implement. One goal of this FLIP is to simplify the process for representing `AnyStruct` as a `String`. Secondly, a customizable `toString` will be useful for future string formatting such as string interpolation with this interface. | |
| This FLIP proposes the addition of a struct interface `StructStringer` to Cadence, which all string-convertible structs will implement. One goal of this FLIP is to simplify the process for representing `AnyStruct` as a `String`. Secondly, a customizable `toString` will be useful for future string formatting such as string interpolation with this interface. |
| With the proposed addition, the code could be simplified to | ||
| ```cadence | ||
| access(all) fun toString(_ value: AnyStruct): String? { | ||
| if let stringerValue = value as ? {StructStringer} { |
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Suggested change
| if let stringerValue = value as ? {StructStringer} { | |
| if let stringerValue = value as? {StructStringer} { |
| } | ||
| } | ||
| ``` | ||
| Additionally a conforming `Struct` can be converted to a `String` in the same function which was not previously possible. This can be useful for various string formatting functions. |
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| Additionally a conforming `Struct` can be converted to a `String` in the same function which was not previously possible. This can be useful for various string formatting functions. | |
| Additionally a conforming struct can be converted to a `String` in the same function which was not previously possible. This can be useful for various string formatting functions. |
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| ### Alternatives Considered | ||
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| An alternative is to have `AnyStruct` itself implement a `toString` function. As a native function there is no longer any risk of malicious code and it still solves the first goal. Additionally, it still allows for more powerful string formatting. The downside of this approach is in limiting customizability for developers. |
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This might be infeasible, given that not all values of AnyStruct are stringable.
| view fun toString(): String | ||
| } | ||
| ``` | ||
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Maybe add a note regarding naming, i.e. why the name of the interface has the prefix Struct
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| - [Display trait](https://doc.rust-lang.org/std/fmt/trait.Display.html) in Rust | ||
| - `Stringer` in Go |
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Suggested change
| - [Display trait](https://doc.rust-lang.org/std/fmt/trait.Display.html) in Rust | |
| - `Stringer` in Go | |
| - [`Display` trait](https://doc.rust-lang.org/std/fmt/trait.Display.html) in Rust | |
| - [`Stringer` interface](https://pkg.go.dev/fmt#Stringer) in Go | |
| - [`CustomStringConvertible`](https://developer.apple.com/documentation/swift/customstringconvertible) in Swift |
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Flip #293 working towards onflow/cadence#3579.