The field 'Property__c' either does not exist on the Offer__c object or it is not a Master-Detail relationship. 

何で間違えているのが理解できないので英語で回答する前に日本語でも回答を書けません。
どうやったら間違うのかが不思議です。


# Property__cは作る必要がある。

https://trailhead.salesforce.com/modules/data_modeling/units/objects_intro

![image.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/328136/d7bdc882-2d24-4c59-9e2e-367677a6f5cd.png)




+ [I can not complete the challenge below as Property doesn't appear in the drop down pick list after selecting Master- Detail relationship. Am I missing something?  ](https://trailhead.salesforce.com/trailblazer-community/feed/0D5KX00000SXpys)

:::note
In this situation you need to follow below steps:- 

Firstly create a new playground Now create a Custom object called Offer and create another Custom object called Property in Object Manager In Property custom object create Look-up relationship for Contact and then in Offer custom object create Main- detail relationship for property and look-up for contacts as well. 


https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000HFODX
:::




# とりあえず見つけたら記録して傾向を調べます。

+ [2024/12/25 The field 'Contact__c' either does not exist on the Offer__c object or it is not a lookup relationship.
Cómo resuelvo?](https://trailhead.salesforce.com/trailblazer-community/feed/0D5KX00000KB1HS)

:::note
上記の解決策を見つけました。正しい手順に従ったにもかかわらず、既存のプレイグラウンドでは機能しません。新しいプレイグラウンドでのみ正しく機能します。そのため、カスタム オブジェクト オファーを作成し、この関係を連絡先とプロパティの両方にマップする必要があります。 
:::

+ [2024/08/01 「プロパティ」の作成と削除のプロセスを何度か実行しましたが、それでも「関連先」ドロップダウンに表示されないようです。](https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007eqYvh)

+ [2023/11/16解決Create Object Relationships - Lookup/Master Relationships](https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007RHHke)

:::note
. I found out the issue. I was creating my Master & Lookup relationship in the wrong custom object. It was supposed to be in the "Offer" object that I made previously. 
:::

+ [2023/09/04解決](https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007FUpix)

:::note
Could you please make sure that you are checking challenge against correct Playground.
:::

+ [2022/12/09 解決](https://trailhead.salesforce.com/trailblazer-community/feed/0D54S00000JfM7eSAF)

:::note
In this situation you need to follow below steps:-
Firstly create a new playground Now create a Custom object called Offer and create another Custom object called Property in Object Manager In Property custom object create Look-up relationship for Contact and then in Offer custom object create Main- detail relationship for property and look-up for contacts as well. 

https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000HFODX
:::

+ [12月17日正解](https://trailhead.salesforce.com/trailblazer-community/feed/0D54S00000Jfbxd)
+ [2023/01/03正解](https://trailhead.salesforce.com/trailblazer-community/feed/0D54S00000MjmTd)
+ [I don't see "Property" as an option in related to drop down. Why?](https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000HDuGN)
+ [8月20日 8:43:未解決](https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000HFODX)
+ [Unable to Create Master-Detail Relationship for Challenge in Create Object Relationships course](https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000IQ4ef)
この場合は既にレコードがあったので主従関係をつくることができなかったみたいです。

+ [9月14日正解](https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000JdXo0SAF)

The correct settings are:
![image.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/328136/997bf731-f48c-575c-d2bb-1808324e070d.png)

+ [Propertyオブジェクトが無かったというオチ](https://trailhead.salesforce.com/trailblazer-community/feed/0D54S00000JfkcN)

:::note
Make sure the Property object is created using the Object Manager.
I think you created it in the previous assignment.
:::

+ [Offer__cオブジェクトが無かったというオチ](https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000Jyb4eSAB)

+ [I need help in Create Object Relationships with Create a Master-Detail Relationship. There is no property in the Related To](https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000K1ntF)

実際に２つのオブジェクトを作ってみたけど、何にも問題ない。

![image.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/328136/46a1ec4c-cb98-048e-e404-45b78a4cd34e.png)

+ [【11/9未解決】Create objects relations - beginning admin -module 2](https://trailhead.salesforce.com/en/trailblazer-community/feed/0D54S00000Jegms)


# 似たような課題　Favorite　と Property

+ [Problem in playground](https://trailhead.salesforce.com/trailblazer-community/feed/0D54S00000A8j1WSAR)

![image.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/328136/1c52cf70-57d5-51b9-2e1d-683f337dc2c3.png)

Propertyオブジェクトを作ってないのが原因

![image.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/328136/d50e6825-f8f0-542c-6a68-a098795a7571.png)

+ [Offer オブジェクトの関係を作成する](https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007MZ0qc)

# Offer__c がない

+ [Optimize Customer Data with Standard and Custom Objects](https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007XIbRw)

![image.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/328136/ba0fa636-51bd-f04e-e04d-cf109ffaee82.png)

:::note
Could you please make sure that you are checking challenge against correct Playground.
:::

# 外部オブジェクトを指定しているのが違っています。参照関係を選択してください

+ [データモデリング 　オブジェクトリレーションを作成するのハンズオンchallenge](https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007clSbk)


![image.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/328136/1e2db2b1-f69e-2d89-a002-eb9efffcfec7.png)