如何从 UILabel 中删除可选文本

问题描述 投票：0回答：3

运行应用程序时，我尝试删除 

Optional
上的 
UILabel
文本。然而，我已经尝试了很多方法，但
Optional
仍然存在。

重要的是，我从 

JSON
获取了这些值，因此我创建了一个 
Struct
来解码所有这些数据。属性 
ibu
是唯一一个写有 
Optional
的属性，但是如果我删除 
?
，我会在 
JSONDecoder
上收到一个错误，内容如下：

Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "索引 23", intValue: 23), CodingKeys(stringValue: "ibu", intValue: nil)], debugDescription: "预期为 Double 值，但发现为 null。", 底层错误：无））

我该如何解决这个问题？

应用图片： enter image description here

模型文件夹：

  struct Cerveja:Decodable{
        let name:String
        let image_url:String
        let description:String
        let tagline:String
        let abv:Double
        let ibu:Double? //This one that I got the "Optional" written in the UILabel
                        //If I remove the "?" I got the error below
    }

查看文件夹 - 详细信息屏幕：

var item:Cerveja?

override func viewDidLoad() {
    super.viewDidLoad()

    labelName.text = item?.name
    labelDescricao.text = item?.description
    labelAmargor.text = "\(String(describing: item!.ibu))" 
    labelTeorAlc.text = "\(item!.abv)"

    let resource = ImageResource(downloadURL: URL(string: "\(item?.image_url ?? "")")!, cacheKey: item?.image_url)
    imageDetail.kf.setImage(with: resource)
}

网络文件夹：

func getApiData(completion: @escaping ([Cerveja]) -> ()){
    guard let urlString = URL(string: "https://api.punkapi.com/v2/beers") else {
        print("URL Error")
        return
    }
    Alamofire.request(urlString).responseJSON { response in

        if response.data == response.data{
            do{
                let decoder = try JSONDecoder().decode([Cerveja].self, from: response.data!)

                completion(decoder)
            }catch{
        print(error)
            }
        }else{print("API Response is Empty")}

        }
}

JSON：

[
  {
    "id": 1,
    "name": "Buzz",
    "tagline": "A Real Bitter Experience.",
    "first_brewed": "09\/2007",
    "description": "A light, crisp and bitter IPA brewed with English and American hops. A small batch brewed only once.",
    "image_url": "https:\/\/images.punkapi.com\/v2\/keg.png",
    "abv": 4.5,
    "ibu": 60,
    "target_fg": 1010,
    "target_og": 1044,
    "ebc": 20,
    "srm": 10,
    "ph": 4.4,
    "attenuation_level": 75,
    "volume": {
      "value": 20,
      "unit": "liters"
    },
    "boil_volume": {
      "value": 25,
      "unit": "liters"
    },
    "method": {
      "mash_temp": [
        {
          "temp": {
            "value": 64,
            "unit": "celsius"
          },
          "duration": 75
        }
      ],
      "fermentation": {
        "temp": {
          "value": 19,
          "unit": "celsius"
        }
      },
      "twist": null
    },
    "ingredients": {
      "malt": [
        {
          "name": "Maris Otter Extra Pale",
          "amount": {
            "value": 3.3,
            "unit": "kilograms"
          }
        },
        {
          "name": "Caramalt",
          "amount": {
            "value": 0.2,
            "unit": "kilograms"
          }
        },
        {
          "name": "Munich",
          "amount": {
            "value": 0.4,
            "unit": "kilograms"
          }
        }
      ],
      "hops": [
        {
          "name": "Fuggles",
          "amount": {
            "value": 25,
            "unit": "grams"
          },
          "add": "start",
          "attribute": "bitter"
        },
        {
          "name": "First Gold",
          "amount": {
            "value": 25,
            "unit": "grams"
          },
          "add": "start",
          "attribute": "bitter"
        },
        {
          "name": "Fuggles",
          "amount": {
            "value": 37.5,
            "unit": "grams"
          },
          "add": "middle",
          "attribute": "flavour"
        },
        {
          "name": "First Gold",
          "amount": {
            "value": 37.5,
            "unit": "grams"
          },
          "add": "middle",
          "attribute": "flavour"
        },
        {
          "name": "Cascade",
          "amount": {
            "value": 37.5,
            "unit": "grams"
          },
          "add": "end",
          "attribute": "flavour"
        }
      ],
      "yeast": "Wyeast 1056 - American Ale\u2122"
    },
    "food_pairing": [
      "Spicy chicken tikka masala",
      "Grilled chicken quesadilla",
      "Caramel toffee cake"
    ],
    "brewers_tips": "The earthy and floral aromas from the hops can be overpowering. Drop a little Cascade in at the end of the boil to lift the profile with a bit of citrus.",
    "contributed_by": "Sam Mason <samjbmason>"
  },
  {
    "id": 2,
    "name": "Trashy Blonde",
    "tagline": "You Know You Shouldn't",
    "first_brewed": "04\/2008",
    "description": "A titillating, neurotic, peroxide punk of a Pale Ale. Combining attitude, style, substance, and a little bit of low self esteem for good measure; what would your mother say? The seductive lure of the sassy passion fruit hop proves too much to resist. All that is even before we get onto the fact that there are no additives, preservatives, pasteurization or strings attached. All wrapped up with the customary BrewDog bite and imaginative twist.",
    "image_url": "https:\/\/images.punkapi.com\/v2\/2.png",
    "abv": 4.1,
    "ibu": 41.5,
    "target_fg": 1010,
    "target_og": 1041.7,
    "ebc": 15,
    "srm": 15,
    "ph": 4.4,
    "attenuation_level": 76,
    "volume": {
      "value": 20,
      "unit": "liters"
    },
    "boil_volume": {
      "value": 25,
      "unit": "liters"
    },
    "method": {
      "mash_temp": [
        {
          "temp": {
            "value": 69,
            "unit": "celsius"
          },
          "duration": null
        }
      ],
      "fermentation": {
        "temp": {
          "value": 18,
          "unit": "celsius"
        }
      },
      "twist": null
    },
    "ingredients": {
      "malt": [
        {
          "name": "Maris Otter Extra Pale",
          "amount": {
            "value": 3.25,
            "unit": "kilograms"
          }
        },
        {
          "name": "Caramalt",
          "amount": {
            "value": 0.2,
            "unit": "kilograms"
          }
        },
        {
          "name": "Munich",
          "amount": {
            "value": 0.4,
            "unit": "kilograms"
          }
        }
      ],
      "hops": [
        {
          "name": "Amarillo",
          "amount": {
            "value": 13.8,
            "unit": "grams"
          },
          "add": "start",
          "attribute": "bitter"
        },
        {
          "name": "Simcoe",
          "amount": {
            "value": 13.8,
            "unit": "grams"
          },
          "add": "start",
          "attribute": "bitter"
        },
        {
          "name": "Amarillo",
          "amount": {
            "value": 26.3,
            "unit": "grams"
          },
          "add": "end",
          "attribute": "flavour"
        },
        {
          "name": "Motueka",
          "amount": {
            "value": 18.8,
            "unit": "grams"
          },
          "add": "end",
          "attribute": "flavour"
        }
      ],
      "yeast": "Wyeast 1056 - American Ale\u2122"
    },
    "food_pairing": [
      "Fresh crab with lemon",
      "Garlic butter dipping sauce",
      "Goats cheese salad",
      "Creamy lemon bar doused in powdered sugar"
    ],
    "brewers_tips": "Be careful not to collect too much wort from the mash. Once the sugars are all washed out there are some very unpleasant grainy tasting compounds that can be extracted into the wort.",
    "contributed_by": "Sam Mason <samjbmason>"
  },
  {
    "id": 3,
    "name": "Berliner Weisse With Yuzu - B-Sides",
    "tagline": "Japanese Citrus Berliner Weisse.",
    "first_brewed": "11\/2015",
    "description": "Japanese citrus fruit intensifies the sour nature of this German classic.",
    "image_url": "https:\/\/images.punkapi.com\/v2\/keg.png",
    "abv": 4.2,
    "ibu": 8,
    "target_fg": 1007,
    "target_og": 1040,
    "ebc": 8,
    "srm": 4,
    "ph": 3.2,
    "attenuation_level": 83,
    "volume": {
      "value": 20,
      "unit": "liters"
    },
    "boil_volume": {
      "value": 25,
      "unit": "liters"
    },
    "method": {
      "mash_temp": [
        {
          "temp": {
            "value": 60,
            "unit": "celsius"
          },
          "duration": 10
        },
        {
          "temp": {
            "value": 65,
            "unit": "celsius"
          },
          "duration": 30
        },
        {
          "temp": {
            "value": 72,
            "unit": "celsius"
          },
          "duration": 10
        },
        {
          "temp": {
            "value": 78,
            "unit": "celsius"
          },
          "duration": 5
        }
      ],
      "fermentation": {
        "temp": {
          "value": 21,
          "unit": "celsius"
        }
      },
      "twist": "Soured naturally using the kettle souring technique, Yuzu fruit: 50g at middle, Yuzu juice: 200ml at FV"
    },
    "ingredients": {
      "malt": [
        {
          "name": "Propino Pale Malt",
          "amount": {
            "value": 1.63,
            "unit": "kilograms"
          }
        },
        {
          "name": "Wheat Malt",
          "amount": {
            "value": 1.63,
            "unit": "kilograms"
          }
        },
        {
          "name": "Propino Pale Malt for kettle 0.03kg souring",
          "amount": {
            "value": 0.03,
            "unit": "kilograms"
          }
        },
        {
          "name": "Acidulated Malt for kettle souring",
          "amount": {
            "value": 0.03,
            "unit": "kilograms"
          }
        }
      ],
      "hops": [
        {
          "name": "Bramling Cross",
          "amount": {
            "value": 10,
            "unit": "grams"
          },
          "add": "middle",
          "attribute": "bitter"
        }
      ],
      "yeast": "Wyeast 1056 - American Ale\u2122"
    }
ios json swift struct
3个回答
2
投票

使用可选绑定来避免这个问题

使用

if let ibu = item?.ibu {
  labelAmargor.text = "\(String(describing: ibu))" 
}

而不是

labelAmargor.text = "\(String(describing: item!.ibu))"
0
投票

我会推荐零合并运算符（??）。您可以在这里找到详细信息

类测试{ var ibu：双倍？ }

var tt: Test? = Test()
tt?.ibu = 3.14
print(String(describing: tt?.ibu)) // Optional("3.14")
print(tt?.ibu ?? 0) // 3.14
tt?.ibu = nil
print(String(describing: tt?.ibu)) // nil
print(tt?.ibu ?? 0) // 0
0
投票

环球银行金融电信协会5.7

为了避免或删除“可选”文本，当（打印）函数与可选一起使用时，您必须放置一个“！”在容器的末尾（变量常量等）。 示例：

var name:String? = "jack"
print(name!)
//the "!" ^ is the reason for the optional text not to appear.
最新问题
© www.soinside.com 2019 - 2024. All rights reserved.