carinfo = ({self.brand}+""+{self.model}+""+{self.year}) TypeError: unsupported operand type(s) for +: 'set' and 'str'

这个错误的原因是你在字符串拼接时，将一个集合（set）类型的变量与字符串类型的变量相加，导致了类型不匹配的错误。你需要将集合类型转换为字符串类型后再进行字符串拼接。可以使用join()方法将集合中的元素转换为字符串并拼接起来，例如：

carinfo = ''.join([self.brand, self.model, self.year])

这样就可以将三个字符串类型的变量拼接成一个完整的字符串。

相关问题

@Override public MessageData importExcel(MultipartFile file, Integer carId){ try { String fileName = file.getOriginalFilename(); ImportParams params = new ImportParams(); //设置表头和标题所占行数 params.setHeadRows(1); // params.setTitleRows(1); //使用importExcel导入文件 List<CreateTOfficialCarStopWashCostImportReq> fileList = ExcelImportUtil.importExcel(file.getInputStream(), CreateTOfficialCarStopWashCostImportReq.class, params); ArrayList<TOfficialCarStopWashCost> list = new ArrayList<>(); for (CreateTOfficialCarStopWashCostImportReq item : fileList) { list.add(item.toEntity()); } //判断excel是否为空 if (list.isEmpty()) { return MessageData.buildFailed("excel为空！"); } for (TOfficialCarStopWashCost item : list) { if(carId==null){ CarInfo carInfo = carInfoMapper.queryByPlateNumber(item.getLicensePlate()); if(carInfo!=null){ item.setCarId(carInfo.getId()); } }else{ item.setCarId(carId); } item.setCreateTime(new Date()); item.setCreateUserId(ShiroUtil.getUserId()); MessageData save = this.save(item); } return MessageData.buildSuccess(); }catch (Exception e) { return MessageData.buildFailed("导入出错了!"); } } 翻译代码

这是一个Java代码，其中定义了一个名为 "importExcel" 的方法，它接受两个参数：一个名为 "file" 的MultipartFile类型的文件和一个名为 "carId" 的Integer类型的汽车ID。该方法的主要功能是从Excel文件中读取数据，并将其转换为TOfficialCarStopWashCost对象的列表，然后将每个对象保存到数据库中。如果传入的carId为null，则该方法会通过车牌号查找对应的carId。如果导入过程中出现错误，则返回一个包含错误信息的MessageData对象。

WARNINGS: ?: (staticfiles.W004) The directory 'static' in the STATICFILES_DIRS setting does not exist. buy.Cart: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'. HINT: Configure the DEFAULT_AUTO_FIELD setting or the BuyConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.d b.models.BigAutoField'. buy.Orders: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'. HINT: Configure the DEFAULT_AUTO_FIELD setting or the BuyConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.d b.models.BigAutoField'. sale.Brand: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'. HINT: Configure the DEFAULT_AUTO_FIELD setting or the SaleConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django. db.models.BigAutoField'. sale.Carinfo: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'. HINT: Configure the DEFAULT_AUTO_FIELD setting or the SaleConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django. db.models.BigAutoField'. userinfo.UserInfo: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'. HINT: Configure the DEFAULT_AUTO_FIELD setting or the UserinfoConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'dja ngo.db.models.BigAutoField'. No changes detected

The warnings indicate the following issues:

- `staticfiles.W004`: The `STATICFILES_DIRS` setting is configured to use a directory named `static`, but it does not exist in your project. You should either create the directory or modify the setting to use an existing directory.

- `models.W042`: Auto-created primary keys are being used for several of your models (`buy.Cart`, `buy.Orders`, `sale.Brand`, `sale.Carinfo`, `userinfo.UserInfo`). You should explicitly define a primary key field for each model instead of relying on the default auto-generated primary key. To do this, add a `primary_key=True` argument to a field in the model definition, or specify a custom primary key field using the `primary_key` attribute.

- `No changes detected`: This is not a warning, but rather an informational message indicating that no changes were detected in your models that require migration.

To address the `models.W042` warnings, you can either add a `primary_key=True` argument to an existing field or create a new field with the `primary_key=True` argument. For example:

class Cart(models.Model):
    cart_id = models.AutoField(primary_key=True)
    # ...

Alternatively, you can configure the `DEFAULT_AUTO_FIELD` setting in your project settings to specify a custom primary key field for all models in your project. For example:

# settings.py
from django.conf import settings

class BuyConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'

settings.configure(BUY_CONFIG=BuyConfig)

This will set the default auto-generated primary key field for all models in the `buy` app to `BigAutoField`. You can repeat this pattern for other apps in your project as well.