首页 \ 问答 \ 传递新道具时，React子组件状态不会更新(React child component state not updating when new props are passed)

传递新道具时，React子组件状态不会更新(React child component state not updating when new props are passed)

 我正在渲染一个自定义模态组件，该组件基于从父组件传入的props显示。 prop isVisible最初为false ，然后通过按钮在父组件中更新。 我正在通过render函数中的console.log语句检查组件状态。 首次初始化组件时，它会按预期记录false false ，但是当更新isVisible时，它返回false true 。 为什么州不用道具更新？  
class MyModal extends React.Component {
  constructor(props) {
    super(props);
      this.state = {
        createModalVisible:props.isVisible,
      };

   setCreateModalVisible = (visible) => {
     this.setState({createModalVisible:visible});
   }

   componentWillMount(){
     this.setCreateModalVisible(this.props.isVisible);
   }

  }
  render() {
    console.log(this.state.createModalVisible,this.props.isVisible);

    return (//modal stuff)
  }
}
export default MyModal
 
 我知道这可能是相当基本的组件生命周期的东西，但我无法从文档中找到它，而且对于React来说还是比较新的。 

I'm rendering a custom modal component that is displayed based on props passed in from a parent component. The prop isVisible is initially false and then updated in the parent component via a button. I'm checking the component state via the console.log statement in the render function. When the component is first initialized, it logs false false as expected but when the isVisible is updated, it returns false true. Why is the state not updating with the props?  
class MyModal extends React.Component {
  constructor(props) {
    super(props);
      this.state = {
        createModalVisible:props.isVisible,
      };

   setCreateModalVisible = (visible) => {
     this.setState({createModalVisible:visible});
   }

   componentWillMount(){
     this.setCreateModalVisible(this.props.isVisible);
   }

  }
  render() {
    console.log(this.state.createModalVisible,this.props.isVisible);

    return (//modal stuff)
  }
}
export default MyModal
 
I get that this is probably pretty basic component lifecycle stuff but I couldn't figure it out from the docs and am fairly new to React.

原文：https://stackoverflow.com/questions/45528800

更新时间：2023-04-17 17:04

最满意答案

 您设置了一个GDT，它具有代码的32位描述符和数据的32位描述符。 在保护模式下，寄存器CS / DS / ES / SS / FS / GS不再是在实模式下看到的段寄存器。 在保护模式下，它们包含一个指向GDT（或LDT）中的条目的选择器。 此代码加载数据寄存器：  
mov ax, DATA_DESC       ; set data segments to data selector (0x10)
mov ds, ax
mov ss, ax
mov es, ax
 
 您不能像这样设置CS寄存器。 FAR jmp可以设置所需的代码段选择器，并在一条指令中设置偏移量。 这就是这个指令的作用：  
jmp CODE_DESC:Stage3
 
 您的GDT设置了代码和数据描述符，这些描述符是4GB平面内存模型，其中基数为0x00000000，限制为0xffffffff。 这意味着一旦处于保护模式并且您正在使用指向这些描述符的选择器，您可以直接从0x00000000到0xffffffff访问所有内存。 这意味着你需要做的就是jmp 0x100000跳转到内存地址0x100000。 在您的代码中，您将不仅要使用0x100000作为跳转位置，还要使用内存副本用作其基础的内存位置。  
 考虑到这一点，简单的解决方法是改变：  
IMAGE_PMODE_BASE equ 0x1000
 
 至：  
IMAGE_PMODE_BASE equ 0x100000

You set up a GDT that has a 32-bit Descriptor for code and 32-bit descriptor for data. In protected mode the registers CS/DS/ES/SS/FS/GS are no longer segment registers in the sense they were seen in real mode. In protected mode they contain a selector that points to an entry in the GDT (or an LDT). This code loads the data registers: 
mov ax, DATA_DESC       ; set data segments to data selector (0x10)
mov ds, ax
mov ss, ax
mov es, ax
 
You can't set the CS register like this. A FAR jmp can set both the code segment selector you want and sets the offset in one instruction. That is what this instruction does: 
jmp CODE_DESC:Stage3
 
Your GDT is set up with code and data descriptors that are a 4gb flat memory model where the base is 0x00000000 and limit is 0xffffffff. This means once in protected mode and you are using selectors that point at these descriptors you can access all memory directly from 0x00000000 to 0xffffffff. This means that all you need to do is jmp 0x100000 to jump to memory address 0x100000. In your code you'll want to use 0x100000 as not only the place to jump to but also the memory location your memory copy uses as its base.  
With that in mind, the simple fix is to change: 
IMAGE_PMODE_BASE equ 0x1000
 
to: 
IMAGE_PMODE_BASE equ 0x100000

传递新道具时，React子组件状态不会更新(React child component state not updating when new props are passed)

最满意答案

相关问答

短地址模式和长寻址模式之间有什么区别(What is the difference between short adressing mode and long addressing mode)[2023-08-13]

间接/索引寻址模式(Indirect/Indexed Addressing Mode)[2024-01-10]

保护模式寻址(Protected Mode Addressing)[2024-03-14]

装配PC相对寻址模式(Assembly PC Relative Addressing Mode)[2022-06-18]

ld，add和rjmp指令的寻址模式是什么？(What is the addressing mode for ld, add, and rjmp instructions?)[2022-10-14]

我们如何在Linux 2.6中从保护模式切换到实模式？(How do we shift from protected mode to real mode in Linux 2.6?)[2022-09-11]

有关寻址模式的查询(Query regarding addressing modes)[2023-07-08]

索引寻址模式和隐含寻址模式(Indexed addressing mode and implied addressing mode)[2022-09-12]

间接寻址模式(Indirect Addressing Mode)[2022-11-21]

寄存器寻址模式与直接寻址模式(Register addressing mode vs Direct addressing mode)[2023-03-18]

相关文章

最新问答