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juce_Result.h
1 
2 /** @weakgroup juce_core-misc
3  * @{
4  */
5 /*
6  ==============================================================================
7 
8  This file is part of the JUCE library.
9  Copyright (c) 2017 - ROLI Ltd.
10 
11  JUCE is an open source library subject to commercial or open-source
12  licensing.
13 
14  The code included in this file is provided under the terms of the ISC license
15  http://www.isc.org/downloads/software-support-policy/isc-license. Permission
16  To use, copy, modify, and/or distribute this software for any purpose with or
17  without fee is hereby granted provided that the above copyright notice and
18  this permission notice appear in all copies.
19 
20  JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
21  EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
22  DISCLAIMED.
23 
24  ==============================================================================
25 */
26 
27 namespace juce
28 {
29 
30 //==============================================================================
31 /**
32  Represents the 'success' or 'failure' of an operation, and holds an associated
33  error message to describe the error when there's a failure.
34 
35  E.g.
36  @code
37  Result myOperation()
38  {
39  if (doSomeKindOfFoobar())
40  return Result::ok();
41  else
42  return Result::fail ("foobar didn't work!");
43  }
44 
45  const Result result (myOperation());
46 
47  if (result.wasOk())
48  {
49  ...it's all good...
50  }
51  else
52  {
53  warnUserAboutFailure ("The foobar operation failed! Error message was: "
54  + result.getErrorMessage());
55  }
56  @endcode
57 
58  @tags{Core}
59 */
61 {
62 public:
63  //==============================================================================
64  /** Creates and returns a 'successful' result. */
65  static Result ok() noexcept { return Result(); }
66 
67  /** Creates a 'failure' result.
68  If you pass a blank error message in here, a default "Unknown Error" message
69  will be used instead.
70  */
71  static Result fail (const String& errorMessage) noexcept;
72 
73  //==============================================================================
74  /** Returns true if this result indicates a success. */
75  bool wasOk() const noexcept;
76 
77  /** Returns true if this result indicates a failure.
78  You can use getErrorMessage() to retrieve the error message associated
79  with the failure.
80  */
81  bool failed() const noexcept;
82 
83  /** Returns true if this result indicates a success.
84  This is equivalent to calling wasOk().
85  */
86  operator bool() const noexcept;
87 
88  /** Returns true if this result indicates a failure.
89  This is equivalent to calling failed().
90  */
91  bool operator!() const noexcept;
92 
93  /** Returns the error message that was set when this result was created.
94  For a successful result, this will be an empty string;
95  */
96  const String& getErrorMessage() const noexcept;
97 
98  //==============================================================================
99  Result (const Result&);
100  Result& operator= (const Result&);
101  Result (Result&&) noexcept;
102  Result& operator= (Result&&) noexcept;
103 
104  bool operator== (const Result& other) const noexcept;
105  bool operator!= (const Result& other) const noexcept;
106 
107 private:
108  String errorMessage;
109 
110  // The default constructor is not for public use!
111  // Instead, use Result::ok() or Result::fail()
112  Result() noexcept;
113  explicit Result (const String&) noexcept;
114 
115  // These casts are private to prevent people trying to use the Result object in numeric contexts
116  operator int() const;
117  operator void*() const;
118 };
119 
120 } // namespace juce
121 
122 /** @}*/
Represents the 'success' or 'failure' of an operation, and holds an associated error message to descr...
Definition: juce_Result.h:61
static Result ok() noexcept
Creates and returns a 'successful' result.
Definition: juce_Result.h:65
The JUCE String class!
Definition: juce_String.h:43
#define JUCE_API
This macro is added to all JUCE public class declarations.