小编Koa*_*orm的帖子

我需要使用boto3更新我的dynamodb表中的timestamp属性,但属性名称"timestamp"是一个保留字,因此它在SET命令上抛出错误.

table.update_item(
    Key={
        'id': item_id
    },
    UpdateExpression='SET timestamp = :val1', # this is the line giving the problem
    ExpressionAttributeValues={
        ":val1": new_timestamp
    }
)

"errorMessage":"调用UpdateItem操作时发生错误(ValidationException):无效的UpdateExpression:属性名称是保留关键字;保留关键字:timestamp",

使用react-native时,我在启动命令时遇到错误.第63行的文件 projectName /node_modules/@babel/core/lib/transformation/file/file.js给出了错误

constructor(options, {
                     ^

SyntaxError: Unexpected token {
    at exports.runInThisContext (vm.js:53:16)
    at Module._compile (module.js:374:25)
    at Module._extensions..js (module.js:417:10)
    at Object.require.extensions.(anonymous function) [as .js] (/home/cread/WHOOP-ReactNative/whoopApp/node_modules/babel-register/lib/node.js:152:7)
    at Module.load (module.js:344:32)
    at Function.Module._load (module.js:301:12)
    at Module.require (module.js:354:17)
    at require (internal/module.js:12:17)
    at Object.<anonymous> (/home/cread/WHOOP-ReactNative/whoopApp/node_modules/@babel/core/lib/index.js:123:36)
    at Module._compile (module.js:410:26)

这是我的package.json文件

{
  "name": *name*,
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "start": "node node_modules/react-native/local-cli/cli.js start",
    "test": "jest"
  },
  "dependencies": {
    "react": "16.3.0-alpha.2",
    "react-native": "0.54.2",
    "react-native-elements": "^0.19.1",
    "react-native-keyboard-aware-scroll-view": "^0.5.0",
    "react-native-modal-dropdown": "^0.6.2",
    "react-native-sound": "0.10.9",
    "react-native-vector-icons": "^4.5.0",
    "react-navigation": "^1.5.8"
  },
  "devDependencies": …

我有一个班级如

class Stuff
{
private:
int x;
virtual int buisness()
{
  return 42;
}
public:
 Stuff(){
  x = 5;
}

给出指向此类实例的指针

Stuff stuff;
void* thing = &stuff;

如何使用指针"thing"获取指向变量x的指针和指向该类的虚函数表的指针？

编辑:澄清这是一个发送给我的挑战,我已经确信这不是一个技巧问题.