QJSEngine Class

  QJSEngine myEngine;
  QJSValue three = myEngine.evaluate("1 + 2");

  QJSValue fun = myEngine.evaluate("(function(a, b) { return a + b; })");
  QJSValueList args;
  args << 1 << 2;
  QJSValue threeAgain = fun.call(QJSValue(), args);

  QString fileName = "helloworld.qs";
  QFile scriptFile(fileName);
  if (!scriptFile.open(QIODevice::ReadOnly))
      // handle error
  QTextStream stream(&scriptFile);
  QString contents = stream.readAll();
  scriptFile.close();
  myEngine.evaluate(contents, fileName);

  myEngine.globalObject().setProperty("myNumber", 123);
  ...
  QJSValue myNumberPlusOne = myEngine.evaluate("myNumber + 1");

  QJSValue result = myEngine.evaluate(...);
  if (result.isError())
      qDebug()
              << "Uncaught exception at line"
              << result.property("lineNumber").toInt()
              << ":" << result.toString();

  QPushButton *button = new QPushButton;
  QJSValue scriptButton = myEngine.newQObject(button);
  myEngine.globalObject().setProperty("button", scriptButton);

  myEngine.evaluate("button.checkable = true");

  qDebug() << scriptButton.property("checkable").toBool();
  scriptButton.property("show").call(); // call the show() slot

成员函数

QJSEngine::QJSEngine()

Constructs a QJSEngine object.

The globalObject() is initialized to have properties as described in ECMA-262, Section 15.1.

QJSEngine::QJSEngine(QObject *parent)

Constructs a QJSEngine object with the given parent.

The globalObject() is initialized to have properties as described in ECMA-262, Section 15.1.

[virtual] QJSEngine::~QJSEngine()

Destroys this QJSEngine.

Garbage is not collected from the persistent JS heap during QJSEngine destruction. If you need all memory freed, call collectGarbage manually right before destroying the QJSEngine.

void QJSEngine::collectGarbage()

Runs the garbage collector.

The garbage collector will attempt to reclaim memory by locating and disposing of objects that are no longer reachable in the script environment.

Normally you don't need to call this function; the garbage collector will automatically be invoked when the QJSEngine decides that it's wise to do so (i.e. when a certain number of new objects have been created). However, you can call this function to explicitly request that garbage collection should be performed as soon as possible.

QJSValue QJSEngine::evaluate(const QString &program, const QString &fileName = QString(), int lineNumber = 1)

Evaluates program, using lineNumber as the base line number, and returns the result of the evaluation.

The script code will be evaluated in the context of the global object.

The evaluation of program can cause an exception in the engine; in this case the return value will be the exception that was thrown (typically an Error object; see QJSValue::isError()).

lineNumber is used to specify a starting line number for program; line number information reported by the engine that pertains to this evaluation will be based on this argument. For example, if program consists of two lines of code, and the statement on the second line causes a script exception, the exception line number would be lineNumber plus one. When no starting line number is specified, line numbers will be 1-based.

fileName is used for error reporting. For example, in error objects the file name is accessible through the "fileName" property if it is provided with this function.

Note: If an exception was thrown and the exception value is not an Error instance (i.e., QJSValue::isError() returns false), the exception value will still be returned, but there is currently no API for detecting that an exception did occur in this case.

T QJSEngine::fromScriptValue(const QJSValue &value)

Returns the given value converted to the template type T.

参见 toScriptValue().

QJSValue QJSEngine::globalObject() const

Returns this engine's Global Object.

By default, the Global Object contains the built-in objects that are part of ECMA-262, such as Math, Date and String. Additionally, you can set properties of the Global Object to make your own extensions available to all script code. Non-local variables in script code will be created as properties of the Global Object, as well as local variables in global code.

void QJSEngine::installExtensions(Extensions extensions, const QJSValue &object = QJSValue())

Installs JavaScript extensions to add functionality that is not available in a standard ECMAScript implementation.

The extensions are installed on the given object, or on the Global Object if no object is specified.

Several extensions can be installed at once by OR-ing the enum values:

  installExtensions(QJSEngine::TranslationExtension | QJSEngine::ConsoleExtension);

This function was introduced in Qt 5.6.

参见 Extension.

QJSValue QJSEngine::newArray(uint length = 0)

Creates a JavaScript object of class Array with the given length.

参见 newObject().

QJSValue QJSEngine::newObject()

Creates a JavaScript object of class Object.

The prototype of the created object will be the Object prototype object.

参见 newArray() and QJSValue::setProperty().

QJSValue QJSEngine::newQMetaObject(const QMetaObject *metaObject)

Creates a JavaScript object that wraps the given QMetaObject The metaObject must outlive the script engine. It is recommended to only use this method with static metaobjects.

When called as a constructor, a new instance of the class will be created. Only constructors exposed by Q_INVOKABLE will be visible from the script engine.

This function was introduced in Qt 5.8.

参见 newQObject().

QJSValue QJSEngine::newQMetaObject()

Creates a JavaScript object that wraps the static QMetaObject associated with class T.

This function was introduced in Qt 5.8.

参见 newQObject().

QJSValue QJSEngine::newQObject(QObject *object)

Creates a JavaScript object that wraps the given QObject object, using JavaScriptOwnership.

Signals and slots, properties and children of object are available as properties of the created QJSValue.

If object is a null pointer, this function returns a null value.

If a default prototype has been registered for the object's class (or its superclass, recursively), the prototype of the new script object will be set to be that default prototype.

If the given object is deleted outside of the engine's control, any attempt to access the deleted QObject's members through the JavaScript wrapper object (either by script code or C++) will result in a script exception.

参见 QJSValue::toQObject().

QJSValue QJSEngine::toScriptValue(const T &value)

Creates a QJSValue with the given value.

参见 fromScriptValue().