source/modules/water/misc/Result.h

   1 /*
   2   ==============================================================================
   3
   4    This file is part of the Water library.
   5    Copyright (c) 2016 ROLI Ltd.
   6    Copyright (C) 2017-2022 Filipe Coelho <falktx@falktx.com>
   7
   8    Permission is granted to use this software under the terms of the ISC license
   9    http://www.isc.org/downloads/software-support-policy/isc-license/
  10
  11    Permission to use, copy, modify, and/or distribute this software for any
  12    purpose with or without fee is hereby granted, provided that the above
  13    copyright notice and this permission notice appear in all copies.
  14
  15    THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
  16    TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
  17    FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
  18    OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
  19    USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  20    TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
  21    OF THIS SOFTWARE.
  22
  23   ==============================================================================
  24 */
  25
  26 #ifndef WATER_RESULT_H_INCLUDED
  27 #define WATER_RESULT_H_INCLUDED
  28
  29 #include "../water.h"
  30
  31 #include <string>
  32
  33 namespace water {
  34
  35 //==============================================================================
  36 /**
  37     Represents the 'success' or 'failure' of an operation, and holds an associated
  38     error message to describe the error when there's a failure.
  39
  40     E.g.
  41     @code
  42     Result myOperation()
  43     {
  44         if (doSomeKindOfFoobar())
  45             return Result::ok();
  46         else
  47             return Result::fail ("foobar didn't work!");
  48     }
  49
  50     const Result result (myOperation());
  51
  52     if (result.wasOk())
  53     {
  54         ...it's all good...
  55     }
  56     else
  57     {
  58         warnUserAboutFailure ("The foobar operation failed! Error message was: "
  59                                 + result.getErrorMessage());
  60     }
  61     @endcode
  62 */
  63 class Result
  64 {
  65 public:
  66     //==============================================================================
  67     /** Creates and returns a 'successful' result. */
  68     static Result ok() noexcept                         { return Result(); }
  69
  70     /** Creates a 'failure' result.
  71         If you pass a blank error message in here, a default "Unknown Error" message
  72         will be used instead.
  73     */
  74     static Result fail (const std::string& errorMessage) noexcept;
  75
  76     //==============================================================================
  77     /** Returns true if this result indicates a success. */
  78     bool wasOk() const noexcept;
  79
  80     /** Returns true if this result indicates a failure.
  81         You can use getErrorMessage() to retrieve the error message associated
  82         with the failure.
  83     */
  84     bool failed() const noexcept;
  85
  86     /** Returns true if this result indicates a success.
  87         This is equivalent to calling wasOk().
  88     */
  89     operator bool() const noexcept;
  90
  91     /** Returns true if this result indicates a failure.
  92         This is equivalent to calling failed().
  93     */
  94     bool operator!() const noexcept;
  95
  96     /** Returns the error message that was set when this result was created.
  97         For a successful result, this will be an empty string;
  98     */
  99     const std::string& getErrorMessage() const noexcept;
 100
 101     //==============================================================================
 102     Result (const Result&);
 103     Result& operator= (const Result&);
 104
 105     bool operator== (const Result& other) const noexcept;
 106     bool operator!= (const Result& other) const noexcept;
 107
 108 private:
 109     std::string errorMessage;
 110
 111     // The default constructor is not for public use!
 112     // Instead, use Result::ok() or Result::fail()
 113     Result() noexcept;
 114     explicit Result (const std::string&) noexcept;
 115
 116     // These casts are private to prevent people trying to use the Result object in numeric contexts
 117     operator int() const;
 118     operator void*() const;
 119 };
 120
 121 }
 122
 123 #endif // WATER_RESULT_H_INCLUDED