1 | /****************************************************************************
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2 | **
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3 | ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
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4 | ** All rights reserved.
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7 | ** This file is part of the documentation of the Qt Toolkit.
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28 | ** GNU General Public License Usage
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29 | ** Alternatively, this file may be used under the terms of the GNU
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38 | ** $QT_END_LICENSE$
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39 | **
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40 | ****************************************************************************/
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41 |
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42 | /*!
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43 | \example script/customclass
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44 | \title Custom Script Class Example
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45 |
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46 | The Custom Script Class example shows how to use QScriptClass and QScriptClassPropertyIterator
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47 | to implement a custom script class.
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48 |
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49 | The script class we are going to implement is called \c{ByteArray}. It provides a wrapper around
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50 | the QByteArray class in Qt, with a simplified API. Why do we need such a class? Well, neither the
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51 | ECMAScript \c{Array} class or \c{String} class is appropriate to use when working with arrays of
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52 | bytes. Our \c{ByteArray} class will have the right semantics; objects will use only the amount of
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53 | memory that is really needed (a byte is stored as a byte, not as a floating-point number or a
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54 | Unicode character) and can be passed directly to C++ slots taking QByteArray arguments (no costly
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55 | conversion necessary).
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56 |
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57 | \section1 ByteArray Class In Use
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58 |
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59 | When the \c{ByteArray} class has been made available to the
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60 | scripting environment, \c{ByteArray} objects can be constructed like
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61 | so:
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62 |
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63 | \snippet doc/src/snippets/code/doc_src_examples_qtscriptcustomclass.qdoc 0
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64 |
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65 | \c{ByteArray} objects behave similar to normal \c{Array} objects. Every \c{ByteArray} object has
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66 | a \c{length} property, that holds the length of the array. If a new value is assigned to the \c{length}
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67 | property, the array is resized. If the array is enlarged, the new bytes are initialized to 0.
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68 | (This is a difference from normal \c{Array} objects; \c{ByteArray} objects are always dense arrays.)
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69 | Use normal array operations to read or write bytes in the array. The following code sets all the
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70 | bytes of an array to a certain value:
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71 |
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72 | \snippet doc/src/snippets/code/doc_src_examples_qtscriptcustomclass.qdoc 1
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73 |
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74 | When assigning a value to an array element, the value is truncated to eight bits:
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75 |
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76 | \snippet doc/src/snippets/code/doc_src_examples_qtscriptcustomclass.qdoc 2
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77 |
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78 | Like normal \c{Array} objects, if the array index is greater than the current length
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79 | of the array, the array is resized accordingly:
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80 |
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81 | \snippet doc/src/snippets/code/doc_src_examples_qtscriptcustomclass.qdoc 3
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82 |
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83 | Property names that aren't valid array indexes are treated
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84 | like normal object properties (again, the same is the case for normal \c{Array} objects);
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85 | in other words, it's perfectly fine to do something like this:
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86 |
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87 | \snippet doc/src/snippets/code/doc_src_examples_qtscriptcustomclass.qdoc 4
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88 |
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89 | The above assignment won't affect the contents of the array, but will rather assign a value
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90 | to the object property named "foo".
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91 |
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