2020-05-26 15:27:50 +00:00
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# 默认值
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你可以为输入值类型定义默认值,下面展示了在不同类型上默认值的定义方法。
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## 对象字段参数
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```rust
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use async_graphql::*;
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struct Query;
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fn my_default() -> i32 {
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30
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}
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2020-09-13 04:12:32 +00:00
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#[GQLObject]
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2020-05-26 15:27:50 +00:00
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impl Query {
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// value参数的默认值为0,它会调用i32::default()
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fn test1(&self, #[arg(default)] value: i32) {}
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// value参数的默认值为10
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fn test2(&self, #[arg(default = 10)] value: i32) {}
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// value参数的默认值使用my_default函数的返回结果,值为30
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fn test3(&self, #[arg(default_with = "my_default()")] value: i32) {}
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}
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```
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## 接口字段参数
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```rust
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use async_graphql::*;
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2020-09-13 04:12:32 +00:00
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#[derive(GQLInterface)]
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#[graphql(
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2020-05-26 15:27:50 +00:00
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field(name = "test1", arg(name = "value", default)),
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field(name = "test2", arg(name = "value", default = 10)),
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field(name = "test3", arg(name = "value", default = "my_default()")),
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)]
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enum MyInterface {
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MyObj(MyObj),
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}
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```
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## 输入对象(InputObject)
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```rust
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use async_graphql::*;
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2020-09-13 04:12:32 +00:00
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#derive(GQLInputObject)
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2020-05-26 15:27:50 +00:00
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struct MyInputObject {
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#[field(default)]
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value1: i32,
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#[field(default = 10)]
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value2: i32,
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#[field(default = "my_default()")]
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value3: i32,
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}
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```
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