{"id":5024,"date":"2022-03-31T16:11:11","date_gmt":"2022-03-31T08:11:11","guid":{"rendered":"https:\/\/1989lifejourney.com\/?p=5024"},"modified":"2022-03-31T16:11:11","modified_gmt":"2022-03-31T08:11:11","slug":"ios-dispatchworkitem","status":"publish","type":"post","link":"https:\/\/1989lifejourney.com\/?p=5024","title":{"rendered":"IOS DispatchWorkItem"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">Definition:<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The work you want to perform, encapsulated in a way that lets you attach a completion handle or execution dependencies.<br>A DispatchWorkItem encapsulates work to be performed on a dispatch queue or within a dispatch group. You can also use a work item as a DispatchSource event, registration, or cancellation handler.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Note: <\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">WorkItem\u7684\u529f\u80fd\u5c31\u662f\u628a\u4e00\u9805\u53ef\u80fd\u91cd\u8907\u57f7\u884c\u7684task\u5c01\u88dd\u8d77\u4f86\uff0c\u4e14\u80fd\u5728multithread\u4e0a\u57f7\u884c(p.s. \u900f\u904eDispatchQueue or DispatchGroup)\u4e26\u5177\u5099\u540c\u6b65\u3001\u53d6\u6d88\u7684\u529f\u80fd\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">WorkItem\u7684\u64cd\u4f5c\u90fd\u53ea\u91dd\u5c0d\u55ae\u4e00task\uff0c\u5982\u679c\u540c\u6642\u8981\u7ba1\u7406\u591a\u500btask\uff0c\u5247\u9084\u662f\u8981\u4f7f\u7528DispatchGroup or DispatchSemaphore\u4f86\u7ba1\u7406\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Function:<\/h2>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>Creating a Work Item<\/strong><\/li><li><strong>Executing the Work Item<\/strong><\/li><li><strong>Adding a Completion Handler<\/strong><\/li><li><strong>Waiting for the Completion of a Work Item<\/strong><\/li><li><strong>Canceling a Work Item<\/strong><\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>Sample code:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\" style=\"font-size:18px;\"><code><strong>\/\/ Creating a Work Item\n<\/strong>let workItem = DispatchWorkItem {\n    print(\"This is my task\")\n}\n\n<strong>\/\/ Executing the Work Item\n<\/strong>workItem.perform()\nDispatchQueue.global().async(execute: workItem)\n\n<strong>\/\/ Waiting for the Completion of a Work Item\n<\/strong>workItem.wait()\n\n<strong>\/\/ Canceling a Work Item\n<\/strong>workItem.cancel()\n\n<strong>\/\/ Adding a Completion Handler\n<\/strong>workItem.notify(queue: DispatchQueue.main) {\n    print(\"Finish executing work item\")\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ref: <a href=\"https:\/\/developer.apple.com\/documentation\/dispatch\/dispatchworkitem\">https:\/\/developer.apple.com\/documentation\/dispatch\/dispatchworkitem<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Definition: The work you want to perform, encapsulated  [&hellip;]<\/p>\n","protected":false},"author":139426785,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","_postgate_lock_override":"inherit","_postgate_lock_mode":"inherit","_postgate_preview_mode":"inherit","_postgate_preview_limit":0,"_postgate_product_ids":[],"advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"jetpack_seo_schema_type":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":true,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_wpcom_ai_launchpad_first_post":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"{title}\n\n{excerpt}\n\n{url}","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"_wpas_customize_per_network":false,"jetpack_post_was_ever_published":false},"categories":[37324612,1],"tags":[],"post_folder":[],"class_list":["post-5024","post","type-post","status-publish","format-standard","hentry","category-ios-development","category-uncategorized"],"jetpack_publicize_connections":[],"jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paR5vw-1j2","jetpack-related-posts":[{"id":4774,"url":"https:\/\/1989lifejourney.com\/?p=4774","url_meta":{"origin":5024,"position":0},"title":"IOS DispatchGroup","author":"Kevin","date":"11 3 \u6708, 2022","format":false,"excerpt":"DispatchGroup A group of tasks that you monitor as\u2026","rel":"","context":"\u5728\u300cIOS Development\u300d\u4e2d","block_context":{"text":"IOS Development","link":"https:\/\/1989lifejourney.com\/?cat=37324612"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":8228,"url":"https:\/\/1989lifejourney.com\/?p=8228","url_meta":{"origin":5024,"position":1},"title":"Software team","author":"Kevin","date":"28 6 \u6708, 2023","format":false,"excerpt":"\u4e0d\u540c\u5de5\u7a0b\u5e2b\u968e\u5c64\u5b9a\u7fa9 Staff Engineer(or Principal Engineer or \u2026","rel":"","context":"\u5728\u300cTechnology sharing\u300d\u4e2d","block_context":{"text":"Technology sharing","link":"https:\/\/1989lifejourney.com\/?cat=55138170"},"img":{"alt_text":"","src":"https:\/\/mermaid.ink\/svg\/pako:eNqN00tvwjAMAOC_EuUM4s5hEs8xRsej2ynl4KWGZqQJMqkY6vjvS9NN2oMKcokbu58cKS65tCnyLt9oe5QZkGPPw8Qwv3oitht3BELWI5kph9KtWbt9x_pihpAyDbTFFpM232t89wHZw6HtEHLmazOjJGi2J_vmfzysa7QfgLkYaFukrKr9lViJPsgdmgupoRgrykM7_3IDEdlXpS9kRmJM1rj2RXImlr2fpy9iUXfLIjCwRaqv20tMnZ-Hz0W5IGWk2vvbjcxWGUQ61wWLquAjlhmmhcbOsgCt3KmzQq3A9-fjD7YsYzTKUmdaVNv5G18FPG7G4xvw5wZ8GPBJMz65bj802INgj5vt8Q2N3zfgo4BPm_HpdfuxwZ4FOyr9I6je8xcYXQef_oC8xXOkHFTqB6msmIS7DHNMeNeHKdAu4Ymp6qBwNj4ZybuOCmzxYp-Cw6GCLUHOuxvQB3-KqXKWonoyw4CePwECjDgq","width":350,"height":200,"srcset":"https:\/\/mermaid.ink\/svg\/pako:eNqN00tvwjAMAOC_EuUM4s5hEs8xRsej2ynl4KWGZqQJMqkY6vjvS9NN2oMKcokbu58cKS65tCnyLt9oe5QZkGPPw8Qwv3oitht3BELWI5kph9KtWbt9x_pihpAyDbTFFpM232t89wHZw6HtEHLmazOjJGi2J_vmfzysa7QfgLkYaFukrKr9lViJPsgdmgupoRgrykM7_3IDEdlXpS9kRmJM1rj2RXImlr2fpy9iUXfLIjCwRaqv20tMnZ-Hz0W5IGWk2vvbjcxWGUQ61wWLquAjlhmmhcbOsgCt3KmzQq3A9-fjD7YsYzTKUmdaVNv5G18FPG7G4xvw5wZ8GPBJMz65bj802INgj5vt8Q2N3zfgo4BPm_HpdfuxwZ4FOyr9I6je8xcYXQef_oC8xXOkHFTqB6msmIS7DHNMeNeHKdAu4Ymp6qBwNj4ZybuOCmzxYp-Cw6GCLUHOuxvQB3-KqXKWonoyw4CePwECjDgq 1x, https:\/\/mermaid.ink\/svg\/pako:eNqN00tvwjAMAOC_EuUM4s5hEs8xRsej2ynl4KWGZqQJMqkY6vjvS9NN2oMKcokbu58cKS65tCnyLt9oe5QZkGPPw8Qwv3oitht3BELWI5kph9KtWbt9x_pihpAyDbTFFpM232t89wHZw6HtEHLmazOjJGi2J_vmfzysa7QfgLkYaFukrKr9lViJPsgdmgupoRgrykM7_3IDEdlXpS9kRmJM1rj2RXImlr2fpy9iUXfLIjCwRaqv20tMnZ-Hz0W5IGWk2vvbjcxWGUQ61wWLquAjlhmmhcbOsgCt3KmzQq3A9-fjD7YsYzTKUmdaVNv5G18FPG7G4xvw5wZ8GPBJMz65bj802INgj5vt8Q2N3zfgo4BPm_HpdfuxwZ4FOyr9I6je8xcYXQef_oC8xXOkHFTqB6msmIS7DHNMeNeHKdAu4Ymp6qBwNj4ZybuOCmzxYp-Cw6GCLUHOuxvQB3-KqXKWonoyw4CePwECjDgq 1.5x, https:\/\/mermaid.ink\/svg\/pako:eNqN00tvwjAMAOC_EuUM4s5hEs8xRsej2ynl4KWGZqQJMqkY6vjvS9NN2oMKcokbu58cKS65tCnyLt9oe5QZkGPPw8Qwv3oitht3BELWI5kph9KtWbt9x_pihpAyDbTFFpM232t89wHZw6HtEHLmazOjJGi2J_vmfzysa7QfgLkYaFukrKr9lViJPsgdmgupoRgrykM7_3IDEdlXpS9kRmJM1rj2RXImlr2fpy9iUXfLIjCwRaqv20tMnZ-Hz0W5IGWk2vvbjcxWGUQ61wWLquAjlhmmhcbOsgCt3KmzQq3A9-fjD7YsYzTKUmdaVNv5G18FPG7G4xvw5wZ8GPBJMz65bj802INgj5vt8Q2N3zfgo4BPm_HpdfuxwZ4FOyr9I6je8xcYXQef_oC8xXOkHFTqB6msmIS7DHNMeNeHKdAu4Ymp6qBwNj4ZybuOCmzxYp-Cw6GCLUHOuxvQB3-KqXKWonoyw4CePwECjDgq 2x, https:\/\/mermaid.ink\/svg\/pako:eNqN00tvwjAMAOC_EuUM4s5hEs8xRsej2ynl4KWGZqQJMqkY6vjvS9NN2oMKcokbu58cKS65tCnyLt9oe5QZkGPPw8Qwv3oitht3BELWI5kph9KtWbt9x_pihpAyDbTFFpM232t89wHZw6HtEHLmazOjJGi2J_vmfzysa7QfgLkYaFukrKr9lViJPsgdmgupoRgrykM7_3IDEdlXpS9kRmJM1rj2RXImlr2fpy9iUXfLIjCwRaqv20tMnZ-Hz0W5IGWk2vvbjcxWGUQ61wWLquAjlhmmhcbOsgCt3KmzQq3A9-fjD7YsYzTKUmdaVNv5G18FPG7G4xvw5wZ8GPBJMz65bj802INgj5vt8Q2N3zfgo4BPm_HpdfuxwZ4FOyr9I6je8xcYXQef_oC8xXOkHFTqB6msmIS7DHNMeNeHKdAu4Ymp6qBwNj4ZybuOCmzxYp-Cw6GCLUHOuxvQB3-KqXKWonoyw4CePwECjDgq 3x"},"classes":[]},{"id":12189,"url":"https:\/\/1989lifejourney.com\/?p=12189","url_meta":{"origin":5024,"position":2},"title":"App vs AI agent","author":"Kevin","date":"19 7 \u6708, 2025","format":false,"excerpt":"The first thing I did this morning was argue with \u2026","rel":"","context":"\u5728\u300cAI related\u300d\u4e2d","block_context":{"text":"AI related","link":"https:\/\/1989lifejourney.com\/?cat=763194612"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":276,"url":"https:\/\/1989lifejourney.com\/?p=276","url_meta":{"origin":5024,"position":3},"title":"AVFoundation Programming Guide &#8211; Swift &#8211; Using Assets","author":"Kevin","date":"25 12 \u6708, 2019","format":false,"excerpt":"Using Assets Assets can come from a file or from m\u2026","rel":"","context":"\u5728\u300cIOS Development\u300d\u4e2d","block_context":{"text":"IOS Development","link":"https:\/\/1989lifejourney.com\/?cat=37324612"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":5758,"url":"https:\/\/1989lifejourney.com\/?p=5758","url_meta":{"origin":5024,"position":4},"title":"\u95dc\u65bc\u5957\u4ef6\u7ba1\u7406\u5de5\u5177(Package manager):","author":"Kevin","date":"22 7 \u6708, 2022","format":false,"excerpt":"\u95dc\u65bc\u5957\u4ef6\u7ba1\u7406\u5de5\u5177(Package manager): About RubyGems:RubyGems\u2026","rel":"","context":"\u5728\u300cTechnology sharing\u300d\u4e2d","block_context":{"text":"Technology sharing","link":"https:\/\/1989lifejourney.com\/?cat=55138170"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":4307,"url":"https:\/\/1989lifejourney.com\/?p=4307","url_meta":{"origin":5024,"position":5},"title":"IOS Grand Central Dispatch(GCD)","author":"Kevin","date":"8 2 \u6708, 2022","format":false,"excerpt":"Grand Central Dispatch(GCD): Dispatch, also known \u2026","rel":"","context":"\u5728\u300cIOS Development\u300d\u4e2d","block_context":{"text":"IOS Development","link":"https:\/\/1989lifejourney.com\/?cat=37324612"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=\/wp\/v2\/posts\/5024","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=\/wp\/v2\/users\/139426785"}],"replies":[{"embeddable":true,"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=5024"}],"version-history":[{"count":3,"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=\/wp\/v2\/posts\/5024\/revisions"}],"predecessor-version":[{"id":5027,"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=\/wp\/v2\/posts\/5024\/revisions\/5027"}],"wp:attachment":[{"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5024"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5024"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5024"},{"taxonomy":"post_folder","embeddable":true,"href":"https:\/\/1989lifejourney.com\/index.php?rest_route=%2Fwp%2Fv2%2Fpost_folder&post=5024"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}