The QScriptContext class represents a Qt Script function invocation. 更多...
The QScriptContext class represents a Qt Script function invocation.
A QScriptContext provides access to the `this' object and arguments passed to a script function. You typically want to access this information when you're writing a native (C++) function (see QScriptEngine.newFunction ()) that will be called from script code. For example, when the script code
foo(20.5, "hello", new Object())
is evaluated, a QScriptContext will be created, and the context will carry the arguments as QScriptValues; in this particular case, the arguments will be one QScriptValue containing the number 20.5, a second QScriptValue containing the string "hello" , and a third QScriptValue containing a Qt Script 对象。
使用 argumentCount () to get the number of arguments passed to the function, and argument () to get an argument at a certain index. The argumentsObject () function returns a Qt Script array object containing all the arguments; you can use the QScriptValueIterator to iterate over its elements, or pass the array on as arguments to another script function using QScriptValue.call ().
使用 thisObject () 到 get the `this' object associated with the function call, and setThisObject () 到 set the `this' object. If you are implementing a native "instance method", you typically fetch the thisObject () and access one or more of its properties:
QScriptValue Person_prototype_fullName(QScriptContext *context, QScriptEngine *engine) { QScriptValue self = context->thisObject(); QString result; result += self.property("firstName").toString(); result += QLatin1String(" "); result += self.property("lastName").toString(); return result; }
使用 isCalledAsConstructor () to determine if the function was called as a constructor (e.g. "new foo()" (as constructor) or just "foo()" ). When a function is called as a constructor, the thisObject () contains the newly constructed object that the function is expected to initialize.
使用 throwValue () 或 throwError () to throw an exception.
使用 callee () to obtain the QScriptValue that represents the function being called. This can for example be used to call the function recursively.
使用 parentContext () to get a pointer to the context that precedes this context in the activation stack. This is mostly useful for debugging purposes (e.g. when constructing some form of backtrace).
activationObject () function returns the object that is used to hold the local variables associated with this function call. You can replace the activation object by calling setActivationObject (). A typical usage of these functions is when you want script code to be evaluated in the context of the parent context, e.g. to implement an include() function:
QScriptValue myInclude(QScriptContext *ctx, QScriptEngine *eng) { QString fileName = ctx->argument(0).toString(); QString contents = readTheFile(fileName); ctx->setActivationObject(ctx->parentContext()->activationObject()); ctx->setThisObject(ctx->parentContext()->thisObject()); return eng->evaluate(contents, fileName); }
使用 backtrace () 到 get a human-readable backtrace associated with this context. This can be useful for debugging purposes when implementing native functions. The toString () function provides a string representation of the context. ( QScriptContextInfo provides more detailed debugging-related information about the QScriptContext.)
使用 engine () to obtain a pointer to the QScriptEngine that this context resides in.
This enum specifies types of error.
| 常量 | 值 | 描述 |
|---|---|---|
| QScriptContext.ReferenceError | 1 | A reference error. |
| QScriptContext.SyntaxError | 2 | A syntax error. |
| QScriptContext.TypeError | 3 | A type error. |
| QScriptContext.RangeError | 4 | A range error. |
| QScriptContext.URIError | 5 | A URI error. |
| QScriptContext.UnknownError | 0 | An unknown error. |
This enum specifies the frameution state of the context.
| 常量 | 值 | 描述 |
|---|---|---|
| QScriptContext.NormalState | 0 | The context is in a normal state. |
| QScriptContext.ExceptionState | 1 | The context is in an exceptional state. |
Returns the activation object of this QScriptContext . The activation object provides access to the local variables associated with this context.
注意： The activation object might not be available if there is no active QScriptEngineAgent , as it might be optimized.
另请参阅 setActivationObject (), argument ()，和 argumentsObject ().
Returns the function argument at the given index .
若 index >= argumentCount (), a QScriptValue of the primitive type Undefined is returned.
另请参阅 argumentCount ().
Returns the number of arguments passed to the function in this invocation.
Note that the argument count can be different from the formal number of arguments (the length property of callee ()).
另请参阅 argument ().
Returns the arguments object of this QScriptContext .
The arguments object has properties callee (equal to callee ()) and length (equal to argumentCount ()), and properties 0 , 1 , ..., argumentCount () - 1 that provide access to the argument values. Initially, property P (0 <= P < argumentCount ()) has the same value as argument( P ). In the case when P is less than the number of formal parameters of the function, P shares its value with the corresponding property of the activation object ( activationObject ()). This means that changing this property changes the corresponding property of the activation object and vice versa.
另请参阅 argument () 和 activationObject ().
Returns a human-readable backtrace of this QScriptContext .
Each line is of the form <function-name>(<arguments>)@<file-name>:<line-number> .
To access individual pieces of debugging-related information (for example, to construct your own backtrace representation), use QScriptContextInfo .
另请参阅 QScriptEngine.uncaughtExceptionBacktrace (), QScriptContextInfo ，和 toString ().
Returns the callee. The callee is the function object that this QScriptContext represents an invocation of.
返回 QScriptEngine that this QScriptContext belongs to.
Returns true if the function was called as a constructor (e.g. "new foo()" ); otherwise returns false.
When a function is called as constructor, the thisObject () contains the newly constructed object to be initialized.
注意： This function is only guaranteed to work for a context corresponding to native functions.
Returns the parent context of this QScriptContext .
Sets the activation object of this QScriptContext to be the given activation .
若 activation is not an object, this function does nothing.
注意： For a context corresponding to a JavaScript function, this is only guaranteed to work if there was an QScriptEngineAgent active on the engine while the function was evaluated.
另请参阅 activationObject ().
Sets the `this' object associated with this QScriptContext to be thisObject .
若 thisObject is not an object, this function does nothing.
另请参阅 thisObject ().
Returns the frameution state of this QScriptContext .
Returns the `this' object associated with this QScriptContext .
另请参阅 setThisObject ().
Throws an error with the given text . Returns the created error object.
text will be stored in the message property of the error object.
The error object will be initialized to contain information about the location where the error occurred; specifically, it will have properties lineNumber , fileName and stack . These properties are described in QtScript Extensions to ECMAScript .
另请参阅 throwValue () 和 state ().
这是重载函数。
Throws an error with the given text . Returns the created error object.
另请参阅 throwValue () 和 state ().
Throws an exception with the given value . Returns the value thrown (the same as the argument).
另请参阅 throwError () 和 state ().
Returns a string representation of this context. This is useful for debugging.
该函数在 Qt 4.4 引入。
另请参阅 backtrace ().
