84 lines
1.7 KiB
Markdown
84 lines
1.7 KiB
Markdown
# 字段守卫(Field Guard)
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你可以为`Object`, `SimpleObject`, `ComplexObject`和`Subscription`的字段定义`守卫`，它将在调用字段的 Resolver 函数前执行，如果失败则返回一个错误。
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```rust
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#[derive(Eq, PartialEq, Copy, Clone)]
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enum Role {
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Admin,
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Guest,
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}
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struct RoleGuard {
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role: Role,
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}
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impl RoleGuard {
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fn new(role: Role) -> Self {
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Self { role }
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}
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}
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#[async_trait::async_trait]
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impl Guard for RoleGuard {
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async fn check(&self, ctx: &Context<'_>) -> Result<()> {
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if ctx.data_opt::<Role>() == Some(&self.role) {
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Ok(())
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} else {
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Err("Forbidden".into())
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}
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}
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}
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```
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用`guard`属性使用它：
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```rust
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#[derive(SimpleObject)]
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struct Query {
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/// 只允许Admin访问
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#[graphql(guard = "RoleGuard::new(Role::Admin)")]
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value1: i32,
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/// 允许Admin或者Guest访问
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#[graphql(guard = "RoleGuard::new(Role::Admin).or(RoleGuard::new(Role::Guest))")]
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value2: i32,
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}
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```
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## 从参数中获取值
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有时候守卫需要从字段参数中获取值，你需要像下面这样在创建守卫时传递该参数值：
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```rust
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struct EqGuard {
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expect: i32,
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actual: i32,
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}
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impl EqGuard {
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fn new(expect: i32, actual: i32) -> Self {
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Self { expect, actual }
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}
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}
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#[async_trait::async_trait]
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impl Guard for EqGuard {
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async fn check(&self, _ctx: &Context<'_>) -> Result<()> {
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if self.expect != self.actual {
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Err("Forbidden".into())
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} else {
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Ok(())
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}
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}
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}
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struct Query;
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#[Object]
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impl Query {
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#[graphql(guard = "EqGuard::new(100, value)")]
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async fn get(&self, value: i32) -> i32 {
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value
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}
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}
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``` |