{"id":638,"date":"2015-10-29T00:00:03","date_gmt":"2015-10-28T23:00:03","guid":{"rendered":"http:\/\/kbyte.snowpenguin.org\/portal\/?p=638"},"modified":"2020-09-27T00:36:20","modified_gmt":"2020-09-26T22:36:20","slug":"angular2-single-service-multiple-apps","status":"publish","type":"post","link":"https:\/\/kbyte.snowpenguin.org\/blog\/2015\/10\/29\/angular2-single-service-multiple-apps\/","title":{"rendered":"Angular2: condividere un servizio tra pi\u00f9 apps"},"content":{"rendered":"<p>Anche se lo scopo primario di Angular \u00e8 la realizzazione di&nbsp;applicazioni SPA (Single Page Application), a volte pu\u00f2 essere necessario instanziare pi\u00f9 app nella pagina come se fossero widget e con la possibilit\u00e0 di condividere dati e funzionalit\u00e0.<\/p>\n<p>L&#8217;utilizzo di classi di servizio \u00e8 stato notevolmente semplificato in Angular2, per\u00f2 questi casi rimangono una rogna soprattutto quando \u00e8 necessario iniettare nel servizio alcune dipendenze con la dependency injection.<\/p>\n<p><!--more--><\/p>\n<p>Supponiamo di avere due app Angular2, che d&#8217;ora in poi chiameremo impropriamente widget. Entrambi utilizzano una classe di servizio cos\u00ec definita:<\/p>\n<pre class=\"brush: jscript; title: ; notranslate\" title=\"\">\n\/\/ service.ts\nimport {Injectable, Inject} from 'angular2\/angular2';\nimport {HTTP_BINDINGS, Http} from 'angular2\/http';\n\n@Injectable()\nexport class DataService {\nhttp: Http;\n\nupdated = new EventEmitter();\n\nconstructor(@Inject(Http) http:Http) {\nthis.http = http;\n}\n\n&#x5B;...]\n}\n<\/pre>\n<p>Questo servizio necessita che Angular inietti nel costruttore un oggetto di tipo Http. I widget sono definiti come se fossero normali app:<\/p>\n<pre class=\"brush: jscript; title: ; notranslate\" title=\"\">\n\/\/ widget1.ts\nimport {Component, View, bind} from 'angular2\/angular2';\nimport {HTTP_BINDINGS, Http} from 'angular2\/http';\nimport {DataService} from '.\/service';\n\n@Component({\nselector: 'widget1',\n})\n@View({&#x5B;...]})\nclass Widget1 {\n\ndataService: DataService;\n\nconstructor(dataService: DataService) {\nthis.dataService = dataService;\n}\n\n&#x5B;...]\n}\n<\/pre>\n<p>Ora qui sorgono i problemi, ad ogni invocazione della funzione bootstrap noi creeremo una nuova instanza di DataService, mentre noi vorremmo utilizzarne solo una.<\/p>\n<pre class=\"brush: jscript; title: ; notranslate\" title=\"\">\n\/\/ Creazione prima istanza DataService\nbootstrap(Widget1, &#x5B;\nHTTP_BINDINGS,\nDataService\n]\n);\n\n\/\/ Creazione seconda istanza DataService\nbootstrap(Widget2, &#x5B;\nHTTP_BINDINGS,\nDataService\n]\n);\n<\/pre>\n<p>Fortunatamente possiamo creare un factory per ricevere sempre una sola instanza, come se fosse un singleton:<\/p>\n<pre class=\"brush: jscript; title: ; notranslate\" title=\"\">\n\/\/ service.ts\nvar sdInstance = null;\n\nexport function DataServiceFactory(http:Http) {\nif(sdInstance == null) {\nsdInstance = new DataService(http);\n}\n\nreturn sdInstance;\n}\n<\/pre>\n<p>Ovviamente dobbiamo assicurarci di utilizzare la stessa funzione factory in tutte le attivazioni dei widget:<\/p>\n<pre class=\"brush: jscript; title: ; notranslate\" title=\"\">\n\/\/ Creazione prima istanza DataService\nbootstrap(Widget1, &#x5B;\nHTTP_BINDINGS,\nbind(DataService)\n.toFactory(DataServiceFactory, &#x5B;Http]),\n]\n);\n\n\/\/ Utilizzo instanza creata in precedenza\nbootstrap(Widget2, &#x5B;\nHTTP_BINDINGS,\nbind(DataService)\n.toFactory(DataServiceFactory, &#x5B;Http]),\n]\n);\n<\/pre>\n<p>Questa potrebbe non essere la soluzione ideale, soprattutto perch\u00e9 gli oggetti iniettati nel servizio in realt\u00e0 appartengono solo a una delle applicazioni\/widget Angular, ma \u00e8 un ottimo compromesso di facile applicazione e comprensione per chi si trover\u00e0 a dover poi interpretare il codice.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Anche se lo scopo primario di Angular \u00e8 la realizzazione di&nbsp;applicazioni SPA (Single Page Application), a volte pu\u00f2 essere necessario instanziare pi\u00f9 app nella pagina come se fossero widget e con la possibilit\u00e0 di condividere dati e funzionalit\u00e0. L&#8217;utilizzo di classi di servizio \u00e8 stato notevolmente semplificato in Angular2, per\u00f2 questi casi rimangono una rogna [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[69,70,75],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Angular2: condividere un servizio tra pi\u00f9 apps - Kbyte@Snowpenguin<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/kbyte.snowpenguin.org\/blog\/2015\/10\/29\/angular2-single-service-multiple-apps\/\" \/>\n<meta property=\"og:locale\" content=\"it_IT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Angular2: condividere un servizio tra pi\u00f9 apps - Kbyte@Snowpenguin\" \/>\n<meta property=\"og:description\" content=\"Anche se lo scopo primario di Angular \u00e8 la realizzazione di&nbsp;applicazioni SPA (Single Page Application), a volte pu\u00f2 essere necessario instanziare pi\u00f9 app nella pagina come se fossero widget e con la possibilit\u00e0 di condividere dati e funzionalit\u00e0. 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