C ++在地图中插入unique_ptr
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C++ inserting unique_ptr in map
提问by vigs1990
I have a C++ object of type ObjectArray
我有一个 C++ 类型的对象 ObjectArray
typedef map<int64_t, std::unique_ptr<Class1>> ObjectArray;
What is the syntax to create a unique_ptrto a new object of type Class1and insert it into an object of type ObjectArray?
unique_ptr为类型为新的对象创建 aClass1并将其插入到类型为的对象中的语法是什么ObjectArray？
回答by Andy Prowl
As a first remark, I wouldn't call it ObjectArrayif it is a map and not an array.
首先，ObjectArray如果它是地图而不是数组，我不会调用它。
Anyway, you can insert objects this way:
无论如何，您可以通过以下方式插入对象：
ObjectArray myMap;
myMap.insert(std::make_pair(0, std::unique_ptr<Class1>(new Class1())));
Or this way:
或者这样：
ObjectArray myMap;
myMap[0] = std::unique_ptr<Class1>(new Class1());
The difference between the two forms is that the former will fail if the key 0is already present in the map, while the second one will overwrite its value with the new one.
两种形式的区别在于，如果键0已经存在于映射中，前一种将失败，而第二种形式会用新的键覆盖其值。
In C++14, you may want to use std::make_unique()instead of constructing the unique_ptrfrom a newexpression. For instance:
在 C++14 中，您可能希望使用std::make_unique()而不是unique_ptr从new表达式构造。例如：
myMap[0] = std::make_unique<Class1>();
回答by Saurabh
If you want to add an existing pointer to insert into the map, you will have to use std::move.
如果要添加现有指针以插入到地图中，则必须使用 std::move。
For example:
例如：
std::unique_ptr<Class1> classPtr(new Class1);
myMap.insert(std::make_pair(0,std::move(classPtr)));
回答by antonpp
In addition to previous answers, I wanted to point out that there is also a method emplace(it's convenient when you cannot/don't want to make a copy), so you can write it like this:
除了前面的答案，我想指出还有一个方法emplace（当你不能/不想复制时很方便），所以你可以这样写：
ObjectArray object_array;
auto pointer = std::make_unique<Class1>(...); // since C++14
object_array.emplace(239LL, std::move(pointer));
// You can also inline unique pointer:
object_array.emplace(30LL, std::make_unique<Class1>(...));
