LocalJsonPersist class

Save a simple-object in a file, in UTF-8 Json format.

Use save to save as Json:

var persist = LocalJsonPersist("xyz");
var simpleObj = "Hello";
await persist.saveJson(simpleObj);

Use load to load from Json:

var persist = LocalJsonPersist("xyz");
Object? decoded = await persist.loadJson();

Examples of valid JSON includes: 42 42.5 "abc" 1, 2, 3 "42", 123 {"42": 123}

Examples of invalid JSON includes: 4, 5, 6 // Not valid because Json does not allow two separate objects. 1, 2, 3 // Not valid because Json does not allow comma separated objects. 'abc' // Not valid because string must use double quotes. {42: "123"} // Not valid because a map key must be of type string.

Constructors

LocalJsonPersist(Object dbName, {String? dbSubDir, List<Object>? subDirs})

Saves to appDocsDir/db/${dbName}.json

LocalJsonPersist.from(File file)

Saves to the given file.

Properties

dbName → String?

final

dbSubDir → String?

final

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

subDirs → List<String>?

final

Methods

delete() → Future<bool>

Deletes the file. If the file was deleted, returns true. If the file did not exist, return false.

exists() → Future<bool>

Returns true if the file exist. False, otherwise.

file() → Future<File>

Gets the file.

length() → Future<int>

Returns the file length. If the file doesn't exist, or exists and is empty, returns 0.

load() → Future<Object?>

Loads a simple-object from a JSON file. If the file doesn't exist, returns null. A JSON can be a String, a number, null, true, false, '{' (a map) or ']' (a list). Note: The file must contain a single JSON, and it can't be empty. It can, however simple contain 'null' (without the quotes) which will return null.

loadAsObj() → Future<Map<String, dynamic>?>

Same as load, but expects the file to be a Map<String, dynamic> representing a single object. Will fail if it's not a map. It may return null.

loadAsObjConverting() → Future<Map<String, dynamic>?>

Same as loadConverting, but expects the file to be a Map<String, dynamic> representing a single object. Will fail if it's not a map. It may return null.

loadConverting({required bool isList}) → Future<Object?>

This method can be used if you were using a Json sequence file with a ".db" termination, and wants to convert it to a regular Json file. This only works if your original ".db" file has a single object.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

save(Object? simpleObj) → Future<File>

Saves the given simple object as JSON. If the file exists, it will be overwritten.

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited

Static Properties

appDocDir → Directory?

no setter

defaultDbSubDir ↔ String

The default is saving/loading to/from "appDocsDir/db/". This is not final, so you can change it. Make it an empty string to remove it.

getter/setter pair

Static Methods

decodeJson(Uint8List bytes) → Object?

Decodes a single JSON into a simple object, from the given bytes.

encodeJson(Object? simpleObj) → Uint8List

Decodes a single simple object into a JSON, from the given simpleObj.

pathName(String? dbName, {String? dbSubDir, List<String>? subDirs}) → String

resetFileSystem() → void

setFileSystem(FileSystem fileSystem) → void

You can set a memory file-system in your tests. For example:

simpleObjsToString(List<Object?>? simpleObjs) → String?

Constants

jsonTermination → const String

The default is adding a ".json" termination to the file name.