48 lines
1.7 KiB
Swift
48 lines
1.7 KiB
Swift
// Copyright 2018 Google Inc. All rights reserved.
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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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import Foundation
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public extension Promise {
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/// Validates a fulfilled value or rejects the value if it can not be validated.
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/// - parameters:
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/// - queue: A queue to dispatch on.
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/// - predicate: An expression to validate.
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/// - returns: A new pending promise that gets either resolved with same resolution as `self` or
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/// rejected with `PromiseError.validationFailure` error.
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@discardableResult
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func validate(
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on queue: DispatchQueue = .promises,
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_ predicate: @escaping (Value) -> Bool
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) -> Promise {
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let promise = Promise(objCPromise.__onQueue(
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queue,
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validate: { objCValue in
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guard let value = Promise<Value>.asValue(objCValue) else {
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preconditionFailure("Cannot cast \(type(of: objCValue)) to \(Value.self)")
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}
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#if (swift(>=4.1) || (!swift(>=4.0) && swift(>=3.3)))
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return predicate(value)
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#else
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return ObjCBool(predicate(value))
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#endif // (swift(>=4.1) || (!swift(>=4.0) && swift(>=3.3)))
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}
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))
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// Keep Swift wrapper alive for chained promise until `ObjCPromise` counterpart is resolved.
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objCPromise.__addPendingObject(promise)
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return promise
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}
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}
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