石墨烯:如何共享用于调用不同解析器的方法的模型

Question

我对GraphQL很陌生，想创建一些数据计算API。我已经定义了一些类的方法，我想在我的模式中使用这些方法。以下是一个最低限度的工作示例：

import graphene

class LocationData:
def __init__(self, latitude, longitude, temperature):
self.lat = latitude
self.lng = longitude
self.tmp = temperature
def first_metric(self):
return self.lat + self.lng
def second_metric(self):
return self.lat / self.tmp ** 2

class GeoInput(graphene.InputObjectType):
lat = graphene.Float(required=True)
lng = graphene.Float(required=True)
tmp = graphene.Float(required=True)

class FirstField(graphene.ObjectType):
first_metric = graphene.Float()

class SecondField(graphene.ObjectType):
second_metric = graphene.Float()
third_metric = graphene.Float()

class Query(graphene.ObjectType):
first = graphene.Field(FirstField, geo=GeoInput(required=True))
second = graphene.Field(SecondField, geo=GeoInput(required=True))
def resolve_first(self, info, geo):
data = LocationData(geo.lat, geo.lng, geo.tmp)
return FirstField(first_metric=data.first_metric())
def resolve_second(self, info, geo):
data = LocationData(geo.lat, geo.lng, geo.tmp)
value1 = data.second_metric()
value2 = value1+300
return SecondField(second_metric=value1,
third_metric=value2)

当前查询如下：

query{
first(geo: {lat: 30, lng: 20, tmp:2}){
firstMetric
}
second(geo: {lat: 30, lng: 20, tmp:2}){
secondMetric
thirdMetric
}
}

在这里，我想知道如何共享我的LocationData对象，以便它只初始化一次，并且它的方法可用于两个解析函数？我在一些文档中找不到任何示例。因此，类似或类似于此：

class Query(graphene.ObjectType):
first = graphene.Field(FirstField, geo=GeoInput(required=True))
second = graphene.Field(SecondField, geo=GeoInput(required=True))
data = LocationData(geo.lat, geo.lng, geo.tmp)
def resolve_first(self, info, geo):
return FirstField(first_metric=self.data.first_metric())
def resolve_second(self, info, geo):
value1 = self.data.second_metric()
value2 = value1+300
return SecondField(second_metric=value1,
third_metric=value2)

Answer 1

实现这一点的最简单方法是简单地将所有可能的度量放在同一ObjectType中，并为其分配一个解析器。

class Metrics(graphene.ObjectType):
first_metric = graphene.Float()
second_metric = graphene.Float()
third_metric = graphene.Float()
class Query(graphene.ObjectType):
metrics = graphene.Field(Metrics, geo=GeoInput(required=True))
def resolve_metrics(self, info, geo):
data = LocationData(geo.lat, geo.lng, geo.tmp)
return Metrics(first_metric=data.first_metric(),
second_metric=data.second_metric(),
third_metric=data.second_metric()+300)

为了避免不必要的计算，可以在函数类中添加一个__init__方法，并为每个字段添加解析器。例如：

class Metrics(graphene.ObjectType):
def __init__(self, data):
self.geo_data = data
first_metric = graphene.Float()
second_metric = graphene.Float()
third_metric = graphene.Float()
def resolve_first_metric(self, info):
print 'First'
return self.geo_data.first_metric()
def resolve_second_metric(self, info):
print 'Second'
return self.geo_data.second_metric()
def resolve_third_metric(self, info):
print 'Third'
return self.geo_data.second_metric() + 300
class Query(graphene.ObjectType):
metrics = graphene.Field(Metrics, geo=GeoInput(required=True))
def resolve_metrics(self, info, geo):
data = LocationData(geo.lat, geo.lng, geo.tmp)
return Metrics(data)

如果我们使用执行此查询

query {
metrics (geo: {lat: 30, lng: 20, tmp:2}) {
firstMetric
thirdMetric
}
}

我们得到

{
"data": {
"metrics": {
"firstMetric": 50.0,
"thirdMetric": 307.5
}
}
}

从控制台中，我们可以看到second_metric()没有被调用。

First
Third