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60 lines
2.5 KiB
Markdown
60 lines
2.5 KiB
Markdown
# Content service
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Accesses app-generated data objects via URLs and file downloads.
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## Methods
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`downloadBlob(blob: Blob, fileName: string): void`<br/>
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Starts downloading the data in `blob` to a named file.
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`downloadData(data: any, fileName: string): void`<br/>
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Starts downloading a data object to a named file.
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`downloadJSON(json: any, fileName): void`<br/>
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Starts downloading of JSON data to a named file.
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`createTrustedUrl(blob: Blob): string`<br/>
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Creates a trusted URL to access the data in `blob`.
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## Details
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Use the Content service to deliver data to the user from `Blob` objects.
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The [Blob](https://developer.mozilla.org/en-US/docs/Web/API/Blob) class
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(implemented in the browser, not ADF) represents an array of bytes that you can
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use to construct and store data in any binary format you choose.
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The user can access a Blob either by downloading the byte array as a file or in
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some cases by viewing it directly in the browser via a special URL that references
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the Blob. For example, you could use the Blob interface to construct an image in the
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[PNG format](https://en.wikipedia.org/wiki/Portable_Network_Graphics). Since
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PNG is a format the browser can display, you could use the Blob's URL in an
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<img> element to view the image within the page. Alternatively, you could let
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the user download it as a PNG file.
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The `downloadBlob` method starts a download of the Blob data to the `filename`
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within the user's downloads folder. The other `downloadXXX` methods do the same
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but first convert the supplied data to a Blob before downloading; see the
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[Blob reference page](https://developer.mozilla.org/en-US/docs/Web/API/Blob)
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for details of how a Blob's contents are assembled from the constructor arguments.
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Use `createdTrustedUrl` to generate a URL string for a Blob. The URL refers to
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the Blob as though it were a file but it is actually an object stored in memory,
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so it does not persist across browser sessions. This URL can be used much like any
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other, so you could use it for the `src` attribute of an <img> element or the
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`href` of a download link. Note that while the URL is 'trusted', the data it contains
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is not necessarily trustworthy unless you can vouch for it yourself; be careful that
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the data doesn't expose your app to
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[Cross Site Scripting](https://en.wikipedia.org/wiki/Cross-site_scripting)
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attacks.
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<!-- Don't edit the See also section. Edit seeAlsoGraph.json and run config/generateSeeAlso.js -->
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<!-- seealso start -->
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## See also
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- [Cookie service](cookie.service.md)
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- [Storage service](storage.service.md)
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<!-- seealso end -->
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