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<p dir="auto">Hi James,</p>
<p dir="auto">Good catch. This is a holdover from an older version of the proposal, and is now a typo.<br>
It should be <code style="background-color:#F7F7F7; border-radius:3px; margin:0; padding:0 0.4em" bgcolor="#F7F7F7">var container</code> — the container can be a <code style="background-color:#F7F7F7; border-radius:3px; margin:0; padding:0 0.4em" bgcolor="#F7F7F7">struct</code>, and shouldn’t require reference semantics.</p>
<p dir="auto">— Itai</p>
<p dir="auto">On 8 Jun 2017, at 7:51, James Froggatt via swift-evolution wrote:</p>
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<div style="white-space:normal"><blockquote style="border-left:2px solid #777; color:#777; margin:0 0 5px; padding-left:5px"><p dir="auto">I've just been trying out the new Coding protocol, and was rather surprised when trying to implement the `encode(to encoder: Encoder)` method.<br>
<br>
The Swift evolution proposal provides the following example code:<br>
<br>
public func encode(to encoder: Encoder) throws {<br>
// Generic keyed encoder gives type-safe key access: cannot encode with keys of the wrong type.<br>
let container = encoder.container(keyedBy: CodingKeys.self)<br>
<br>
// The encoder is generic on the key -- free key autocompletion here.<br>
try container.encode(latitude, forKey: .latitude)<br>
try container.encode(longitude, forKey: .longitude)<br>
}<br>
<br>
<br>
Here, container is stored as a `let` value, and uses reference semantics, while the proposal also clearly lists these `encode` methods as mutating. With the current implementation of the proposal, the container must be stored as a `var`, which leads to code like the following:<br>
<br>
var container = encoder.singleValueContainer()<br>
try container.encode(data)<br>
<br>
This clearly wont work as expected if the container were to have value semantics, and writing code like this feels plain wrong. Is SE-0166 really intended to work with referrence-type encoders only?<br>
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</blockquote></div>
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