C++ 如何格式化 QString？
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How to format a QString?
提问by hubert poduszczak
I'd like to format a string for Qt label, I'm programming in C++ on Qt.
我想为 Qt 标签格式化一个字符串，我在 Qt 上用 C++ 编程。
In ObjC I would write something like:
在 ObjC 中，我会写一些类似的东西：
NSString *format=[NSString stringWithFormat: ... ];
How to do something like that in Qt?
如何在 Qt 中做类似的事情？
回答by Dat Chu
You can use QString.arg like this
你可以像这样使用 QString.arg
QString my_formatted_string = QString("%1/%2-%3.txt").arg("~", "Tom", "Jane");
// You get "~/Tom-Jane.txt"
This method is preferred over sprintf because:
这种方法比 sprintf 更受欢迎，因为：
Changing the position of the string without having to change the ordering of substitution, e.g.
改变字符串的位置而不必改变替换的顺序，例如
// To get "~/Jane-Tom.txt"
QString my_formatted_string = QString("%1/%3-%2.txt").arg("~", "Tom", "Jane");
Or, changing the type of the arguments doesn't require changing the format string, e.g.
或者，更改参数的类型不需要更改格式字符串，例如
// To get "~/Tom-1.txt"
QString my_formatted_string = QString("%1/%2-%3.txt").arg("~", "Tom", QString::number(1));
As you can see, the change is minimal. Of course, you generally do not need to care about the type that is passed into QString::arg() since most types are correctly overloaded.
如您所见，变化很小。当然，您通常不需要关心传递给 QString::arg() 的类型，因为大多数类型都已正确重载。
One drawback though: QString::arg() doesn't handle std::string. You will need to call: QString::fromStdString() on your std::string to make it into a QString before passing it to QString::arg(). Try to separate the classes that use QString from the classes that use std::string. Or if you can, switch to QString altogether.
但有一个缺点：QString::arg() 不处理 std::string。在将它传递给 QString::arg() 之前，您需要在 std::string 上调用： QString::fromStdString() 以使其成为 QString。尝试将使用 QString 的类与使用 std::string 的类分开。或者，如果可以，完全切换到 QString。
UPDATE: Examples are updated thanks to Frank Osterfeld.
更新：感谢 Frank Osterfeld 更新了示例。
UPDATE: Examples are updated thanks to alexisdm.
更新：感谢 alexisdm 更新了示例。
回答by trojanfoe
You can use the sprintfmethod, however the argmethod is preferred as it supports unicode.
您可以使用该sprintf方法，但arg首选该方法，因为它支持 unicode。
QString str;
str.sprintf("%s %d", "string", 213);
回答by Stephen Chu
Use QString::arg()for the same effect.
使用QString::arg()相同的效果。
