[英]C++ inserting unique_ptr in map
I have a C++ object of type ObjectArray
我有一个
ObjectArray
类型的C ++对象
typedef map<int64_t, std::unique_ptr<Class1>> ObjectArray;
What is the syntax to create a unique_ptr
to a new object of type Class1
and insert it into an object of type ObjectArray
? 为
Class1
类型的新对象创建unique_ptr
并将其插入ObjectArray
类型的对象的语法是什么?
As a first remark, I wouldn't call it ObjectArray
if it is a map and not an array. 首先,如果它是一个映射而不是一个数组,我不会将其称为
ObjectArray
。
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 0
is already present in the map, while the second one will overwrite its value with the new one. 两种形式之间的区别在于,如果映射中已经存在键
0
,则前一种将失败,而第二种将用新的密钥覆盖其值。
In C++14, you may want to use std::make_unique()
instead of constructing the unique_ptr
from a new
expression. 在C ++ 14中,您可能要使用
std::make_unique()
而不是根据new
表达式构造unique_ptr
。 For instance: 例如:
myMap[0] = std::make_unique<Class1>();
If you want to add an existing pointer to insert into the map, you will have to use std::move. 如果要添加现有的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)));
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: 除了以前的答案,我想指出的是,还有一个方法
emplace
(在您无法/不想进行复制时很方便),因此可以这样编写:
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>(...));
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