1.. title:: clang-tidy - cppcoreguidelines-prefer-member-initializer
2
3cppcoreguidelines-prefer-member-initializer
4===========================================
5
6Finds member initializations in the constructor body which can be  converted
7into member initializers of the constructor instead. This not only improves
8the readability of the code but also positively affects its performance.
9Class-member assignments inside a control statement or following the first
10control statement are ignored.
11
12This check implements `C.49
13<https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c49-prefer-initialization-to-assignment-in-constructors>`_
14from the C++ Core Guidelines.
15
16Please note, that this check does not enforce rule `C.48
17<https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c48-prefer-in-class-initializers-to-member-initializers-in-constructors-for-constant-initializers>`_
18from the C++ Core Guidelines. For that purpose
19see check :doc:`modernize-use-default-member-init <../modernize/use-default-member-init>`.
20
21Example 1
22---------
23
24.. code-block:: c++
25
26  class C {
27    int n;
28    int m;
29  public:
30    C() {
31      n = 1; // Literal in default constructor
32      if (dice())
33        return;
34      m = 1;
35    }
36  };
37
38Here ``n`` can be initialized in the constructor initializer list, unlike
39``m``, as ``m``'s initialization follows a control statement (``if``):
40
41.. code-block:: c++
42
43  class C {
44    int n;
45    int m;
46  public:
47    C(): n(1) {
48      if (dice())
49        return;
50      m = 1;
51    }
52  };
53
54Example 2
55---------
56
57.. code-block:: c++
58
59  class C {
60    int n;
61    int m;
62  public:
63    C(int nn, int mm) {
64      n = nn; // Neither default constructor nor literal
65      if (dice())
66        return;
67      m = mm;
68    }
69  };
70
71Here ``n`` can be initialized in the constructor initializer list, unlike
72``m``, as ``m``'s initialization follows a control statement (``if``):
73
74.. code-block:: c++
75
76  C(int nn, int mm) : n(nn) {
77    if (dice())
78      return;
79    m = mm;
80  }
81