newStruct === void 0 ? void 0 : newStruct.definitions是什么意思
时间: 2024-03-29 07:34:22 浏览: 29
这是一个 JavaScript 的条件运算符(ternary operator),也称为三元运算符。它的含义是:如果 newStruct 的值等于 undefined 或 null,则返回 undefined 或 null;否则返回 newStruct.definitions。
这段代码意味着,如果 newStruct 存在并且其 definitions 属性存在,则返回 definitions 属性的值;否则返回 undefined。这种写法的好处是避免了出现 undefined 或 null 的错误,使代码更加健壮。
相关问题
解释一下这个函数: static mapStruct(struct, mapper, prop) { if (!struct) { return mapper(struct, prop); } let newStruct = mapper(struct, prop); if (!newStruct) { return newStruct; } if (newStruct === null || newStruct === void 0 ? void 0 : newStruct.definitions) { newStruct = Object.assign(Object.assign({}, (newStruct || {})), { definitions: mapObject(newStruct === null || newStruct === void 0 ? void 0 : newStruct.definitions, (val, key) => { return StructOp.mapStruct(val, mapper, key); }) }); } switch (struct === null || struct === void 0 ? void 0 : struct.type) { case "array": { if (struct.items) { return Object.assign(Object.assign({}, newStruct), { items: StructOp.mapStruct(struct.items, mapper) }); } return newStruct; } case "object": { if (newStruct === null || newStruct === void 0 ? void 0 : newStruct.properties) { return Object.assign(Object.assign({}, newStruct), { properties: Object.keys(newStruct.properties || {}).reduce((newProps, prop) => { const propStruct = StructOp.mapStruct(newStruct.properties[prop], mapper, prop); if (propStruct) { return Object.assign(Object.assign({}, newProps), { [prop]: propStruct }); } else { return newProps; } }, {}) }); } if (struct.additionalProperties) { return Object.assign(Object.assign({}, newStruct), { additionalProperties: StructOp.mapStruct(struct.additionalProperties, mapper) }); } } case "boolean": case "integer": case "number": case "string": { return newStruct; } } return newStruct; }
这是一个静态方法,接受三个参数:struct、mapper和prop。它的作用是将一个结构体对象进行映射转换。具体来说,它会先使用mapper函数对结构体对象进行映射转换,得到一个新的结构体对象newStruct。然后根据原结构体对象的类型,对newStruct进行进一步的处理,最后返回处理后的newStruct。
具体来说,如果原结构体对象为null或undefined,直接返回mapper函数对其进行映射转换后的结果。否则,对newStruct进行进一步的处理:
1. 如果newStruct中包含了definitions属性,递归调用mapStruct方法对其进行映射转换,并将转换后的结果赋值给newStruct的definitions属性;
2. 如果原结构体对象的类型为array,且有items属性,则对items属性进行递归调用mapStruct方法进行映射转换,并将转换后的结果赋值给newStruct的items属性;
3. 如果原结构体对象的类型为object,且newStruct中包含了properties属性,则对properties属性进行遍历,递归调用mapStruct方法对每个属性进行映射转换,并将转换后的结果赋值给newProps对象的对应属性。最后将所有转换后的属性保存到newStruct的properties属性中;
4. 如果原结构体对象的类型为object,且有additionalProperties属性,则对additionalProperties属性进行递归调用mapStruct方法进行映射转换,并将转换后的结果赋值给newStruct的additionalProperties属性;
5. 如果原结构体对象的类型为boolean、integer、number或string,则直接返回newStruct。
最后,返回处理后的newStruct。
Which is used to define the member of a class externally? a. : b. :: c. # d. !!$
b. ::
The scope resolution operator `::` is used to define a member of a class externally in C++. This allows the definition of a member function or a static data member to be separate from its declaration in the class definition.
For example:
```
class MyClass {
public:
void myFunction(); // declaration
static int myStaticVariable; // declaration
};
// definition of myFunction
void MyClass::myFunction() {
// function body
}
// definition of myStaticVariable
int MyClass::myStaticVariable = 0;
```
In the example above, `myFunction` and `myStaticVariable` are declared in the class definition, but their definitions are provided externally using the scope resolution operator `::`. This allows the implementation of the member functions and static data members to be separated from the class definition, which can make the code easier to manage and understand.