如何在 C++ Qt 中填充静态 QMap 的值？
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How do I populate values of a static QMap in C++ Qt?
提问by Di Zou
I have this in my C++ header file:
我的 C++ 头文件中有这个：
#include <QMap>
#include <QString>
class LogEvent {
public:
LogEvent();
enum column_t {TIMESTAMP_COLUMN = 0, TYPE_COLUMN = 1, EVENT_COLUMN = 2,
FILE_COLUMN = 3};
static QMap<column_t, QString> COLUMN_NAMES;
static QMap<column_t, QString> getColumnNames() {
return LogEvent::COLUMN_NAMES;
}
//blah blah blah other functions
};
This is my C++ source file:
这是我的 C++ 源文件：
#include "LogEvent.h"
LogEvent::LogEvent()
{
//constructor code
}
//blah blah blah other functions
I want to add values to my static QMap COLUMN_NAMES. Where and how would I do this?
我想向我的静态 QMap COLUMN_NAMES 添加值。我将在哪里以及如何做到这一点？
采纳答案by userr1728854
You can use static function that returns initialized map:
您可以使用返回初始化映射的静态函数：
// source file:
QMap<column_t, QString> LogEvent::initColumnNames() {
QMap<column_t, QString> map;
map.insert(LogEvent::TIMESTAMP_COLUMN,"Timestamp");
// and so on
return map;
}
QMap<column_t, QString> LogEvent::COLUMN_NAMES = initColumnNames();
Also, in case you want to use strings internationalization in static variables and need to call QTextCodec::setCodecForTrfirst, it is a good idea to move static variable into its getter function:
此外，如果您想在静态变量中使用字符串国际化并且需要先调用QTextCodec::setCodecForTr，最好将静态变量移动到其 getter 函数中：
class LogEvent {
public:
// ...
static QMap<column_t, QString> initColumnNames();
static QMap<column_t, QString> getColumnNames() {
static QMap<column_t, QString> COLUMN_NAMES = initColumnNames();
return COLUMN_NAMES;
}
}
This way COLUMN_NAMESwill be initialized with the first call of getColumnNames()and you can set the text codec beforehand. But this is not thread-safe.
这种方式COLUMN_NAMES将在第一次调用时初始化，getColumnNames()您可以预先设置文本编解码器。但这不是线程安全的。
回答by Luchs
In the meantime, Qt 5.2 added support for C++11 initializer lists in QMap:
同时，Qt 5.2 在 QMap 中添加了对 C++11 初始值设定项列表的支持：
QMap::?QMap(std::initializer_list<std::pair<Key, T> > list)
This means you can initialize your map like this:
这意味着您可以像这样初始化您的地图：
static QMap<QString, int> my_map{{"a", 1}, {"b", 2}, {"c", 3}};
回答by Al Conrad
Another approach using an initializer list.
另一种使用初始化列表的方法。
QMap<QString, QString> qmap_(std::map<QString, QString> {{ "", "" }});
This works for older Qt before Qt was fixed to work with initializer lists directly.
在 Qt 被修复为直接使用初始化列表之前，这适用于较旧的 Qt。
回答by fghj
You can create std::map and use it to init QMap, or just replace QMap with std::map:
您可以创建 std::map 并使用它来初始化 QMap，或者只是用 std::map 替换 QMap：
static const std::pair<T1, T2> arr[] = {
std::pair<T1, T2>(v1, v2),
std::pair<T1, T2>(v3, v4),
};
static std::map<T1, T2> my_map(arr, arr + sizeof(arr) / sizeof(arr[0]));
QMap<column_t, QString> LogEvent::COLUMN_NAMES(my_map);
Another way is init COLUMN_NAMES in constructor:
另一种方法是在构造函数中初始化 COLUMN_NAMES：
LogEvent::LogEvent() {
if (COLUMN_NAMES.isEmpty())
;//init it here
but this is not thread safe, the first one method was called before main, while the second during may be called during runtime.
但这不是线程安全的，第一个方法在 main 之前调用，而第二个方法可能在运行时调用。
