| 16 | */ |
| 17 | export const FIELD_PROXY_HANDLER: ProxyHandler<() => FieldNode> = { |
| 18 | get(getTgt: () => FieldNode, property: string | symbol, receiver: Record<string, unknown>) { |
| 19 | if (property === FIELD_TREE) { |
| 20 | return true; |
| 21 | } |
| 22 | |
| 23 | const tgt = getTgt(); |
| 24 | |
| 25 | // First, check whether the requested property is a defined child node of this node. |
| 26 | const child = tgt.structure.getChild(property); |
| 27 | if (child !== undefined) { |
| 28 | // If so, return the child node's `FieldTree` proxy, allowing the developer to continue |
| 29 | // navigating the form structure. |
| 30 | return child.fieldTree; |
| 31 | } |
| 32 | |
| 33 | // Otherwise, we need to consider whether the properties they're accessing are related to array |
| 34 | // iteration. We're specifically interested in `length`, but we only want to pass this through |
| 35 | // if the value is actually an array. |
| 36 | // |
| 37 | // We untrack the value here to avoid spurious reactive notifications. In reality, we've already |
| 38 | // incurred a dependency on the value via `tgt.getChild()` above. |
| 39 | const value = untracked(tgt.value); |
| 40 | |
| 41 | if (isArray(value)) { |
| 42 | // Allow access to the length for field arrays, it should be the same as the length of the data. |
| 43 | if (property === 'length') { |
| 44 | return (tgt.value() as Array<unknown>).length; |
| 45 | } |
| 46 | // Allow access to the iterator. This allows the user to spread the field array into a |
| 47 | // standard array in order to call methods like `filter`, `map`, etc. |
| 48 | if (property === Symbol.iterator) { |
| 49 | return () => { |
| 50 | // When creating an iterator, we need to account for reactivity. The iterator itself will |
| 51 | // read things each time `.next()` is called, but that may happen outside of the context |
| 52 | // where the iterator was created (e.g. with `@for`, actual diffing happens outside the |
| 53 | // reactive context of the template). |
| 54 | // |
| 55 | // Instead, side-effectfully read the value here to ensure iterator creation is reactive. |
| 56 | tgt.value(); |
| 57 | return Array.prototype[Symbol.iterator].apply(tgt.fieldTree); |
| 58 | }; |
| 59 | } |
| 60 | // Note: We can consider supporting additional array methods if we want in the future, |
| 61 | // but they should be thoroughly tested. Just forwarding the method directly from the |
| 62 | // `Array` prototype results in broken behavior for some methods like `map`. |
| 63 | } |
| 64 | |
| 65 | if (isObject(value)) { |
| 66 | // For object fields, allow iteration over their entries for convenience of use with `@for`. |
| 67 | if (property === Symbol.iterator) { |
| 68 | return function* () { |
| 69 | for (const key in receiver) { |
| 70 | yield [key, receiver[key]]; |
| 71 | } |
| 72 | }; |
| 73 | } |
| 74 | } |
| 75 | |