1 /*
2   ==============================================================================
3 
4    This file is part of the JUCE library.
5    Copyright (c) 2020 - Raw Material Software Limited
6 
7    JUCE is an open source library subject to commercial or open-source
8    licensing.
9 
10    The code included in this file is provided under the terms of the ISC license
11    http://www.isc.org/downloads/software-support-policy/isc-license. Permission
12    To use, copy, modify, and/or distribute this software for any purpose with or
13    without fee is hereby granted provided that the above copyright notice and
14    this permission notice appear in all copies.
15 
16    JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
17    EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
18    DISCLAIMED.
19 
20   ==============================================================================
21 */
22 
23 namespace juce
24 {
25 
26 //==============================================================================
27 /**
28     Represents the 'success' or 'failure' of an operation, and holds an associated
29     error message to describe the error when there's a failure.
30 
31     E.g.
32     @code
33     Result myOperation()
34     {
35         if (doSomeKindOfFoobar())
36             return Result::ok();
37         else
38             return Result::fail ("foobar didn't work!");
39     }
40 
41     const Result result (myOperation());
42 
43     if (result.wasOk())
44     {
45         ...it's all good...
46     }
47     else
48     {
49         warnUserAboutFailure ("The foobar operation failed! Error message was: "
50                                 + result.getErrorMessage());
51     }
52     @endcode
53 
54     @tags{Core}
55 */
56 class JUCE_API  Result
57 {
58 public:
59     //==============================================================================
60     /** Creates and returns a 'successful' result. */
ok()61     static Result ok() noexcept                         { return Result(); }
62 
63     /** Creates a 'failure' result.
64         If you pass a blank error message in here, a default "Unknown Error" message
65         will be used instead.
66     */
67     static Result fail (const String& errorMessage) noexcept;
68 
69     //==============================================================================
70     /** Returns true if this result indicates a success. */
71     bool wasOk() const noexcept;
72 
73     /** Returns true if this result indicates a failure.
74         You can use getErrorMessage() to retrieve the error message associated
75         with the failure.
76     */
77     bool failed() const noexcept;
78 
79     /** Returns true if this result indicates a success.
80         This is equivalent to calling wasOk().
81     */
82     operator bool() const noexcept;
83 
84     /** Returns true if this result indicates a failure.
85         This is equivalent to calling failed().
86     */
87     bool operator!() const noexcept;
88 
89     /** Returns the error message that was set when this result was created.
90         For a successful result, this will be an empty string;
91     */
92     const String& getErrorMessage() const noexcept;
93 
94     //==============================================================================
95     Result (const Result&);
96     Result& operator= (const Result&);
97     Result (Result&&) noexcept;
98     Result& operator= (Result&&) noexcept;
99 
100     bool operator== (const Result& other) const noexcept;
101     bool operator!= (const Result& other) const noexcept;
102 
103 private:
104     String errorMessage;
105 
106     // The default constructor is not for public use!
107     // Instead, use Result::ok() or Result::fail()
108     Result() noexcept;
109     explicit Result (const String&) noexcept;
110 
111     // These casts are private to prevent people trying to use the Result object in numeric contexts
112     operator int() const;
113     operator void*() const;
114 };
115 
116 } // namespace juce
117