uniapp 如何用<picker>实现省市区三级联动

肝疼，4 个小时了，弄不出。感觉官网教程用下来完全摸不着头脑。
后端数据如下：
[
{
"name": "浙江",
"code": "zj",
"citys": [
{
"name": "杭州",
"code": "zj-hz",
"districts": [
{
"name": "西湖区",
"code": "zj-hz-xh"
},
{
"name": "滨江区",
"code": "zj-hz-bj"
}
]
},
{
"name": "温州",
"code": "zj-wz",
"districts": [
{
"name": "鹿城区",
"code": "zj-wz-lc"
},
{
"districtName": "瓯海区",
"districtCode": "zj-wz-oh"
}
]
}
]
},
{
"name": "福建",
"code": "fj",
"citys": [
{
"name": "福州",
"code": "fj-fz",
"districts": [
{
"name": "鼓楼区",
"code": "fj-fz-gl"
},
{
"name": "台江区",
"code": "fj-fz-tj"
}
]
},
{
"name": "厦门",
"code": "fj-xm",
"districts": [
{
"name": "思明区",
"code": "fj-xm-sm"
},
{
"districtName": "海沧区",
"districtCode": "fj-xm-hc"
}
]
}
]
}
]