Github user jasongin commented on a diff in the pull request:
https://github.com/apache/cordova-plugin-file/pull/176#discussion_r58442531
--- Diff: README.md ---
@@ -538,3 +540,263 @@ Android also supports a special filesystem named
"documents", which represents a
* `root`: The entire device filesystem
By default, the library and documents directories can be synced to iCloud.
You can also request two additional filesystems, `library-nosync` and
`documents-nosync`, which represent a special non-synced directory within the
`/Library` or `/Documents` filesystem.
+
+## Sample: Create Files and Directories, Write, Read, and Append files ##
+
+The File plugin allows you to do things like store files in a temporary or
persistent storage location for your app (sandboxed storage). The code snippets
in this section demonstrate different tasks including:
+* Accessing the file system
+* Using cross-platform Cordova file URLs to store your files (see _Where
to Store Files_ for more info)
+* Creating files and directories
+* Writing to files
+* Reading files
+* Appending files
+
+## Create a persistent file
+
+Before you can use the File plugin APIs, you must get access to the file
system using `requestFileSystem`. When you do this, you can request either
persistent or temporary storage. Persistent storage will not be removed unless
permission is granted by the user.
+
+When you get file system access, access is granted for the sandboxed file
system only (the sandbox limits access to the app itself), not for general
access to any file system location on the device.
+
+Here is a request for persistent storage.
+
+>*Note* When targeting devices (instead of a browser), you dont need to
use `requestQuota` before using persistent storage.
+
+```
+window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function (fs) {
+
+ console.log('file system open: ' + fs.name);
+ fs.root.getFile("newPersistentFile.txt", { create: true, exclusive:
false }, function (fileEntry) {
+
+ console.log("fileEntry is file?" + fileEntry.isFile.toString());
+ // fileEntry.name == 'someFile.txt'
+ // fileEntry.fullPath == '/someFile.txt'
+ writeFile(fileEntry, null);
+
+ }, onErrorCreateFile);
+
+}, onErrorLoadFs);
+```
+
+The success callback receives FileSystem object (fs). Use `fs.root` to
return a DirectoryEntry object, which you can use to create or get a file (by
calling `getFile`). In this example, `fs.root` is a DirectoryEntry object that
represents the persistent storage in the sandboxed file system.
+
+The success callback for `getFile` receives a FileEntry object. You can
use this to perform file write and file read operations.
+
+## Create a temporary file
+
+Here is an example of a request for temporary storage. Temporary storage
may be deleted by the operating system if the device runs low on memory.
+
+```
+window.requestFileSystem(window.TEMPORARY, 5 * 1024 * 1024, function (fs) {
+
+ console.log('file system open: ' + fs.name);
+ createFile(fs.root, "newTempFile.txt");
+
+}, onErrorLoadFs);
+```
+When you are using temporary storage, you can create or get the file by
calling `getFile`. As in the persistent storage example, this will give you a
FileEntry object that you can use for read or write operations.
+
+```
+// Creates a new file or returns the file if it already exists.
+dirEntry.getFile(fileName, {create: true, exclusive: false},
function(fileEntry) {
+
+ writeFile(fileEntry);
+
+}, onErrorCreateFile);
+```
+
+## Write to a file
+
+Once you have a FileEntry object, you can write to the file by calling
`createWriter`, which returns a FileWriter object in the success callback. Call
the `write` method of FileWriter to write to the file.
+
+```
+function writeFile(fileEntry, dataObj) {
+ // Create a FileWriter object for our FileEntry (log.txt).
+ fileEntry.createWriter(function (fileWriter) {
+
+ fileWriter.onwriteend = function (e) {
+ console.log("Successful file read...");
+ readFile(fileEntry);
+ };
+
+ fileWriter.onerror = function (e) {
+ console.log("Failed file read: " + e.toString());
+ };
+
+ // If data object is not passed in,
+ // create a new Blob instead.
+ if (!dataObj) {
+ dataObj = new Blob(['some file data'], { type: 'text/plain' });
+ }
+
+ fileWriter.write(dataObj);
+ });
+}
+```
+
+## Read a file
+
+You also need a FileEntry object to read an existing file. Use the file
property of FileEntry to get the file reference, and then create a new
FileReader object. You can use methods like `readAsText` to start the read
operation. When the read operation is complete, `this.result` stores the result
of the read operation.
+
+```
+function readFile(fileEntry) {
+ fileEntry.file(function (file) {
+ var reader = new FileReader();
+
+ reader.onloadend = function (e) {
+ console.log("Successful file read: " + this.result);
+ displayFileData(fileEntry.fullPath + ": " + this.result);
+ if (this.result.toString().substring(0, 4) == "blob") {
+ displayImageData(this.result);
+ }
+ };
+
+ reader.readAsText(file);
+
+ }, onErrorReadFile);
+}
+```
+
+## Store an existing file
+
+We already showed how to write to a file that you just created in the
sandboxed file system. What if you need to get access to an existing file and
convert that to something you can store on your device? In this example, you
obtain a file using an xhr request, and then save it to the cache in the
sandboxed file system.
+
+Before you get the file, get a FileSystem reference using
`requestFileSystem`. By passing window.TEMPORARY in the method call (same as
before), the returned FileSystem object (fs) represents the cache in the
sandboxed file system. Call `fs.root` to get the DirectoryEntry object.
+
+```
+window.requestFileSystem(window.TEMPORARY, 5 * 1024 * 1024, function (fs) {
+
+ console.log('file system open: ' + fs.name);
+ getSampleFile(fs.root);
+
+}, onErrorLoadFs);
+```
+
+For completeness, here is the xhr request to get a Blob image. There is
nothing Cordova-specific in this code, except that you forward the
DirectoryEntry reference that you already obtained as an argument to the
saveFile function. You will save the image as a DOM string URL and display it
later after reading the file (to validate the operation).
+
+```
+function getSampleFile(dirEntry) {
+
+ var xhr = new XMLHttpRequest();
+ xhr.open('GET',
'http://cordova.apache.org/static/img/cordova_bot.png', true);
+ xhr.responseType = 'blob';
+
+ xhr.onload = function (e) {
+ if (this.status == 200) {
+
+ var blob = new Blob([this.response], { type: 'image/png' });
+ var img = new Image();
--- End diff --
Why create this Image object? It doesn't seem to be actually used. You
could save the blob directly without using the Image object.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
