The core of passing Props in Vue is that the parent component passes data to the child component through binding properties. The child component must declare Props first before it can be used. 1. The child component is declared in the props option in the form of an object, such as props: { title: String, likes: { type: Number, default: 0 }, isActive: { type: Boolean, required: true }}, which can define types, default values ??and verification rules; 2. The parent component uses v-bind to bind attributes to pass values ??in the template, such as , note that HTML attributes are named with short horizontal lines, and JS uses camel; 3. Common problems include string literals that are not added to add a colon, props Undeclared, typo, or type mismatch, console warnings and props definitions should be checked and debugged with Vue devtools.

Passing props in Vue is the basis of parent-child component communication, and the core lies in the parent component passing data to child components by binding properties. As long as you understand the two links of statement and use, this is actually a very direct process.

How to declare Props in child components

A child component needs to define the props it wants to receive before it can use this data normally. You can write in array or object form in props option. It is recommended to use object writing method, and you can add types, default values ??and even verification rules.

For example:

 props: {
  title: String,
  likes: { type: Number, default: 0 },
  isActive: { type: Boolean, required: true }
}

The advantage of writing this way is that it clearly expresses the requirements of this component for external data, and also avoids runtime errors due to the error type passed.

How to transfer data from the parent component

The parent component only needs to pass the value in the template by binding attributes. For example, the child component is called <PostItem /> , and the parent component can be written like this:

 <PostItem :title="post.title" :likes="post.likes" :is-active="isActive" />

Two things to note here:

• Problems with property names. HTML attributes are case-sensitive, so they should be named with short horizontal lines (such as is-active ) in the template, and camels (such as isActive ) can be used in JS.
• Use v-bind to bind data dynamically. If it is a string literal, you can also not use colons, but in most cases, dynamic binding is still required.

Some FAQs and Suggestions

Sometimes there are cases where props do not take effect, and there may be several reasons:

• Forgot to add a colon : , which causes strings rather than variables to be passed;
• The child component does not declare props correctly;
• The attribute name is spelled incorrectly, such as msg written as mgs ;
• Type mismatch, such as expecting a number but passing a string;

The key to solving these problems is to see if the console has warnings and check whether the child components have correctly defined props. In addition, try to enable Vue's devtools tool during development to facilitate checking whether props are received normally.

Basically that's it. Although it is simple, it is also the most basic part of Vue component design. It is very helpful to understand clearly the more complex communication methods for subsequent processing.

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