The Soql.WhenClause Class

The Soql.WhenClause class is a builder for constructing WHEN clauses in TYPEOF queries. This class provides a fluent interface for specifying which fields to select when a particular SObjectType matches in a polymorphic field query.

This class is designed to work in conjunction with the Soql.TypeOf class and follows the builder pattern to enable method chaining.

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Constructor

WhenClause(Soql.TypeOf parent, SObjectType objectType)

Creates a new WhenClause builder instance. This constructor is private and should not be called directly. Instead, use the when() method on a Soql.TypeOf instance.

Parameters:

• parent - The parent TypeOf instance
• objectType - The SObjectType for this WHEN clause

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Methods

thenSelect

Specifies fields to select for this WHEN clause. All methods return the parent Soql.TypeOf instance to enable continued chaining.

Signatures:

• Soql.TypeOf thenSelect(List<SObjectField> fields)
• Soql.TypeOf thenSelect(SObjectField field)
• Soql.TypeOf thenSelect(SObjectField field1, SObjectField field2)
• Soql.TypeOf thenSelect(SObjectField field1, SObjectField field2, SObjectField field3)
• Soql.TypeOf thenSelect(SObjectField field1, SObjectField field2, SObjectField field3, SObjectField field4)
• Soql.TypeOf thenSelect(SObjectField field1, SObjectField field2, SObjectField field3, SObjectField field4, SObjectField field5)

Parameters:

• fields - List of SObjectFields to select for this WHEN clause
• field, field1, field2, etc. - Individual SObjectFields to select (null values are automatically filtered out)

Returns:

• The parent Soql.TypeOf instance for continued method chaining

Features:

• Null Filtering: Automatically filters out null SObjectField values
• Type Safety: Ensures only valid SObjectFields are included
• Method Chaining: Returns parent TypeOf for continued fluent interface usage

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Usage Examples

Single Field Selection

Soql.TypeOf typeOfClause = new Soql.TypeOf(Task.WhatId)
    .when(Account.SObjectType)
        .thenSelect(Account.Name);

Multiple Field Selection

Soql.TypeOf typeOfClause = new Soql.TypeOf(Task.WhatId)
    .when(Account.SObjectType)
        .thenSelect(Account.Name, Account.Phone, Account.Industry);

List-Based Selection

List<SObjectField> accountFields = new List<SObjectField>{
    Account.Name,
    Account.Phone,
    Account.Type,
    Account.Industry,
    Account.BillingCity
};

Soql.TypeOf typeOfClause = new Soql.TypeOf(Task.WhatId)
    .when(Account.SObjectType)
        .thenSelect(accountFields);

Multiple WHEN Clauses

Soql.TypeOf typeOfClause = new Soql.TypeOf(Task.WhatId)
    .when(Account.SObjectType)
        .thenSelect(Account.Name, Account.Phone)
    .when(Opportunity.SObjectType)
        .thenSelect(Opportunity.Name, Opportunity.StageName, Opportunity.Amount)
    .when(Contact.SObjectType)
        .thenSelect(Contact.FirstName, Contact.LastName, Contact.Email)
    .elseSelect('Name');

Null Field Handling

// Null fields are automatically filtered out
SObjectField nullField = null;
Soql.TypeOf typeOfClause = new Soql.TypeOf(Task.WhatId)
    .when(Account.SObjectType)
        .thenSelect(Account.Name, nullField, Account.Phone); // nullField is ignored

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Design Pattern

The WhenClause class follows the Builder Pattern principles:

1. Fluent Interface: Method chaining enables readable query construction
2. Immutable Operations: Each method call returns the parent object for continued chaining
3. Type Safety: Strong typing with SObjectField parameters prevents runtime errors
4. Defensive Programming: Automatic null filtering prevents invalid field references

Example of Fluent Chaining:

Soql soql = DatabaseLayer.Soql.newQuery(Task.SObjectType)
    .addSelect(
        new Soql.TypeOf(Task.WhatId)
            .when(Account.SObjectType)
                .thenSelect(Account.Name, Account.Phone)
            .when(Opportunity.SObjectType)
                .thenSelect(Opportunity.Name, Opportunity.StageName)
            .elseSelect('Name')
    )
    .addWhere(Task.Subject, Soql.NOT_EQUALS, null)
    .toSoql();

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Related Classes

• Soql.TypeOf - Parent class that creates WhenClause instances
• Soql.Builder - Main query builder that accepts TypeOf clauses
• Soql.Selectable - Interface implemented by TypeOf for builder compatibility