74 lines
3.3 KiB
Swift
74 lines
3.3 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 FBLPromises
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/// Creates a pending promise that fulfills with the same value as the promise returned from `work`
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/// block, which executes asynchronously on the given `queue`, or rejects with the same error after
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/// all retry attempts have been exhausted. On rejection, the `work` block is retried after the
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/// given delay `interval` and will continue to retry until the number of specified attempts have
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/// been exhausted or will bail early if the given condition is not met.
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///
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/// - parameters:
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/// - queue: A queue to invoke the `work` block on.
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/// - count: Max number of retry attempts. The `work` block will be executed once if the specified
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/// count is less than or equal to zero. The default is
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/// `__FBLPromiseRetryDefaultAttemptsCount`.
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/// - interval: Time to wait before the next retry attempt. The default is
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/// `__FBLPromiseRetryDefaultDelayInterval`.
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/// - predicate: Condition to check before the next retry attempt. The block takes the following
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/// parameters:
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/// - count: Number of remaining retry attempts.
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/// - error: The error the promise was rejected with.
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/// - work: A block that executes asynchronously on the given `queue` and returns a value or an
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/// error used to resolve the promise.
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/// - returns: A new pending promise that fulfills with the same value as the promise returned from
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/// `work` block, or rejects with the same error after all retry attempts have been
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/// exhausted or if the given condition is not met.
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public func retry<Value>(
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on queue: DispatchQueue = .promises,
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attempts count: Int = __FBLPromiseRetryDefaultAttemptsCount,
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delay interval: TimeInterval = __FBLPromiseRetryDefaultDelayInterval,
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condition predicate: ((_ count: Int, _ error: Error) -> Bool)? = nil,
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_ work: @escaping () throws -> Promise<Value>
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) -> Promise<Value> {
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#if (swift(>=4.1) || (!swift(>=4.0) && swift(>=3.3)))
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let predicateBlock = predicate
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#else
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var predicateBlock: ((_ count: Int, _ error: Error) -> ObjCBool)?
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if predicate != nil {
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predicateBlock = { count, error -> ObjCBool in
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guard let predicate = predicate else { return true }
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return ObjCBool(predicate(count, error))
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}
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}
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#endif // (swift(>=4.1) || (!swift(>=4.0) && swift(>=3.3)))
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let objCPromise = Promise<Value>.ObjCPromise<AnyObject>.__onQueue(
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queue,
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attempts: count,
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delay: interval,
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condition: predicateBlock
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) {
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do {
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return try work().objCPromise
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} catch let error {
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return error as NSError
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}
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}
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let promise = Promise<Value>(objCPromise)
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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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