61 lines
2.0 KiB
Swift
61 lines
2.0 KiB
Swift
// Copyright 2020 Tokamak contributors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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public protocol EnvironmentKey {
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associatedtype Value
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static var defaultValue: Value { get }
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}
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/// This protocol defines a type which mutates the environment in some way.
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/// Unlike `EnvironmentalModifier`, which reads the environment to
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/// create a `ViewModifier`.
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///
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/// It can be applied to a `View` or `ViewModifier`.
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public protocol _EnvironmentModifier {
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func modifyEnvironment(_ values: inout EnvironmentValues)
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}
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public extension ViewModifier where Self: _EnvironmentModifier {
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static func _makeView(_ inputs: ViewInputs<Self>) -> ViewOutputs {
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var environment = inputs.environment.environment
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inputs.content.modifyEnvironment(&environment)
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return .init(inputs: inputs, environment: environment)
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}
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}
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public struct _EnvironmentKeyWritingModifier<Value>: ViewModifier, _EnvironmentModifier {
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public let keyPath: WritableKeyPath<EnvironmentValues, Value>
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public let value: Value
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public init(keyPath: WritableKeyPath<EnvironmentValues, Value>, value: Value) {
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self.keyPath = keyPath
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self.value = value
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}
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public typealias Body = Never
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public func modifyEnvironment(_ values: inout EnvironmentValues) {
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values[keyPath: keyPath] = value
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}
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}
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public extension View {
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func environment<V>(
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_ keyPath: WritableKeyPath<EnvironmentValues, V>,
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_ value: V
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) -> some View {
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modifier(_EnvironmentKeyWritingModifier(keyPath: keyPath, value: value))
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}
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}
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