|
27 | 27 | const $get = Symbol.for("FluidValue.get"); |
28 | 28 | const $observers = Symbol.for("FluidValue.observers"); |
29 | 29 |
|
| 30 | +/** Returns true if `arg` can be observed. */ |
| 31 | +export const hasFluidValue = (arg: any): arg is FluidValue => Boolean(arg && arg[$get]) |
| 32 | + |
30 | 33 | /** An event sent to `FluidObserver` objects. */ |
31 | 34 | export interface FluidEvent<T = any> { |
32 | 35 | type: string; |
@@ -116,3 +119,69 @@ export function callFluidObservers(target: any, event: FluidEvent) { |
116 | 119 | }); |
117 | 120 | } |
118 | 121 | } |
| 122 | +type GetFluidObservers = { |
| 123 | + <E extends FluidEvent>(target: FluidValue<any, E>): ReadonlySet< |
| 124 | + FluidObserver<E> |
| 125 | + > | null |
| 126 | + (target: object): ReadonlySet<FluidObserver> | null |
| 127 | +} |
| 128 | + |
| 129 | + |
| 130 | +/** Observe a `fluids`-compatible object. */ |
| 131 | +export function addFluidObserver<T, E extends FluidEvent>( |
| 132 | + target: FluidValue<T, E>, |
| 133 | + observer: FluidObserver<E> |
| 134 | +): typeof observer |
| 135 | + |
| 136 | +export function addFluidObserver<E extends FluidEvent>( |
| 137 | + target: object, |
| 138 | + observer: FluidObserver<E> |
| 139 | +): typeof observer |
| 140 | + |
| 141 | +export function addFluidObserver(target: any, observer: FluidObserver) { |
| 142 | + if (target[$get]) { |
| 143 | + let observers: Set<FluidObserver> = target[$observers] |
| 144 | + if (!observers) { |
| 145 | + setHidden(target, $observers, (observers = new Set())) |
| 146 | + } |
| 147 | + if (!observers.has(observer)) { |
| 148 | + observers.add(observer) |
| 149 | + if (target.observerAdded) { |
| 150 | + target.observerAdded(observers.size, observer) |
| 151 | + } |
| 152 | + } |
| 153 | + } |
| 154 | + return observer |
| 155 | +} |
| 156 | + |
| 157 | +/** Stop observing a `fluids`-compatible object. */ |
| 158 | +export function removeFluidObserver<E extends FluidEvent>( |
| 159 | + target: FluidValue<any, E>, |
| 160 | + observer: FluidObserver<E> |
| 161 | +): void |
| 162 | + |
| 163 | +export function removeFluidObserver<E extends FluidEvent>( |
| 164 | + target: object, |
| 165 | + observer: FluidObserver<E> |
| 166 | +): void |
| 167 | + |
| 168 | +export function removeFluidObserver(target: any, observer: FluidObserver) { |
| 169 | + let observers: Set<FluidObserver> = target[$observers] |
| 170 | + if (observers && observers.has(observer)) { |
| 171 | + const count = observers.size - 1 |
| 172 | + if (count) { |
| 173 | + observers.delete(observer) |
| 174 | + } else { |
| 175 | + target[$observers] = null |
| 176 | + } |
| 177 | + if (target.observerRemoved) { |
| 178 | + target.observerRemoved(count, observer) |
| 179 | + } |
| 180 | + } |
| 181 | +} |
| 182 | + |
| 183 | + |
| 184 | +/** Get the current observer set. Never mutate it directly! */ |
| 185 | +export const getFluidObservers: GetFluidObservers = (target: any) => |
| 186 | + target[$observers] || null |
| 187 | + |
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