字段掩码

在 Google Ads API 中，更新是使用字段掩码完成的。字段掩码会列出您打算通过更新更改的所有字段，并且系统会忽略字段掩码中未包含的任何指定字段，即使这些字段已发送到服务器也是如此。

FieldMaskUtil

生成字段掩码的推荐方法是使用我们的内置字段掩码实用程序，您可以通过该实用程序根据修改后的对象生成字段掩码，而无需从头构建。

下面是一个更新广告系列的示例：

// Update campaign by setting its status to paused, and "Search network" to false.
Campaign campaignToUpdate = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
    Status = CampaignStatus.Paused,
    NetworkSettings = new NetworkSettings()
    {
        TargetSearchNetwork = false
    }
};

// Create the operation.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaignToUpdate,
    UpdateMask = FieldMasks.AllSetFieldsOf(campaignToUpdate)
};

// Update the campaign.
MutateCampaignsResponse response = campaignService.MutateCampaigns(
    customerId.ToString(), new CampaignOperation[] { operation });

首先，我们创建一个空的 Campaign 对象。然后，我们设置其资源名称，以便 API 确切知道要更新哪个广告系列。

该示例使用 FieldMasks.AllSetFieldsOf 方法对广告系列自动生成一个字段掩码，用于枚举所有已设置的字段。然后，您可以直接将返回的掩码传递给更新调用。

有时，您可能需要处理现有对象并更新一些字段。在这种情况下，您需要修改代码，如下所示：

Campaign existingCampaign;

// Obtain existingCampaign from elsewhere.
...

// Create a new campaign based off the existing campaign for update.
Campaign campaignToUpdate = new Campaign(existingCampaign);

// Update campaign by setting its status to paused, and "Search network" to
// false.
campaignToUpdate.Status = CampaignStatus.Paused;
campaignToUpdate.NetworkSettings = new NetworkSettings()
{
    TargetSearchNetwork = false
}

// Create the operation.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaignToUpdate,
    UpdateMask = FieldMasks.FromChanges(existingCampaign, campaignToUpdate)
};

如需从头开始创建字段掩码，您需要先创建一个 FieldMask 对象，然后创建一个数组并填充您打算更改的所有字段的名称，最后将数组内容附加到字段掩码的 Path 字段。

FieldMask fieldMask = new FieldMask();
fieldMask.Paths.AddRange(new string[] { "status", "name" });

更新消息字段及其子字段

MESSAGE 字段可以有子字段（例如 MaximizeConversions 有三个子字段：target_cpa_micros、cpc_bid_ceiling_micros 和 cpc_bid_floor_micros），也可以没有子字段（例如 ManualCpm）。

未定义子字段的消息字段

更新未使用任何子字段定义的 MESSAGE 字段时，请使用 FieldMasks 生成字段掩码，如上所述。

包含已定义子字段的消息字段

更新使用子字段定义的 MESSAGE 字段时，如果未在该消息上明确设置任何子字段，则必须手动将每个可变 MESSAGE 子字段添加到 FieldMask，这与从头创建字段掩码的上例类似。

一个常见的示例是，更新广告系列的出价策略，但未在新的出价策略中设置任何字段。以下示例演示了如何更新广告系列以使用 MaximizeConversions 出价策略，而无需为出价策略设置任何子字段。

在这种情况下，使用 FieldMasks 的 AllSetFieldsOf() 和 FromChanges() 方法无法实现预期目标。

以下示例会生成包含 maximize_conversions 的字段掩码。不过，Google Ads API 不允许这种行为，以防止意外清除字段，并会生成 FieldMaskError.FIELD_HAS_SUBFIELDS 错误。

// Creates a campaign with the proper resource name and an empty
// MaximizeConversions field.
Campaign campaign = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
    MaximizeConversions = new MaximizeConversions()
};

// Constructs an operation, using the FieldMasks' AllSetFieldsOf utility to
// derive the update mask. The field mask will include 'maximize_conversions`,
// which will produce a FieldMaskError.FIELD_HAS_SUBFIELDS error.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaign,
    UpdateMask = FieldMasks.AllSetFieldsOf(campaign)
};

// Sends the operation in a mutate request that will result in a
// FieldMaskError.FIELD_HAS_SUBFIELDS error because empty MESSAGE fields cannot
// be included in a field mask.
MutateCampaignsResponse response = campaignService.MutateCampaigns(
    customerId.ToString(), new CampaignOperation[] { operation });

以下示例演示了如何正确更新广告系列以使用 MaximizeConversions 出价策略，而无需设置其任何子字段。

// Creates a Campaign object with the proper resource name.
Campaign campaign = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
};

// Creates a field mask from the existing campaign and adds all of the fields
// on the MaximizeConversions bidding strategy to the field mask. Because these
// fields are included in the field mask but excluded from the campaign object,
// the Google Ads API will set the campaign's bidding strategy to a
// MaximizeConversions object with none of its subfields set.
FieldMask fieldMask = FieldMasks.AllSetFieldsOf(campaign);
// Only include 'maximize_conversions.target_cpa_micros' in the field mask
// as it is the only mutable subfield on MaximizeConversions when used as a
// standard bidding strategy.
//
// Learn more about standard and portfolio bidding strategies here:
// https://developers.google.com/google-ads/api/docs/campaigns/bidding/assign-strategies
fieldMask.Paths.AddRange(new string[] {
    "maximize_conversions.target_cpa_micros",
});

// Creates an operation to update the campaign with the specified fields.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaign,
    UpdateMask = fieldMask
};

清除字段

某些字段可以明确清除。与上述示例类似，您必须将这些字段明确添加到字段掩码中。例如，假设您有一个广告系列使用的是 MaximizeConversions 出价策略，并且 target_cpa_micros 字段的值设为大于 0 的值。

以下代码会运行；不过，系统不会将 maximize_conversions.target_cpa_micros 添加到字段掩码，因此不会对 target_cpa_micros 字段进行任何更改：

// Creates a campaign with the proper resource name and a MaximizeConversions
// object with target_cpa_micros set to 0.
Campaign campaign = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
    MaximizeConversions = new MaximizeConversions()
    {
        TargetCpaMicros = 0
    }
};

// Constructs an operation, using the FieldMasks' AllSetFieldsOf utility to
// derive the update mask. However, the field mask will NOT include
// 'maximize_conversions.target_cpa_micros'.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaign,
    UpdateMask = FieldMasks.AllSetFieldsOf(campaign)
};

// Sends the operation in a mutate request that will succeed but will NOT update
// the 'target_cpa_micros' field because 'maximize_conversions.target_cpa_micros'
// was not included in the field mask.
MutateCampaignsResponse response = campaignService.MutateCampaigns(
    customerId.ToString(), new CampaignOperation[] { operation });

以下示例演示了如何正确清除 MaximizeConversions 出价策略的 target_cpa_micros 字段。

// Creates a Campaign object with the proper resource name.
Campaign campaign = new Campaign()
{
    ResourceName = ResourceNames.Campaign(customerId, campaignId),
};

// Constructs a field mask from the existing campaign and adds the
// 'maximize_conversions.target_cpa_micros' field to the field mask, which will
// clear this field from the bidding strategy without impacting any other fields
// on the bidding strategy.
FieldMask fieldMask = FieldMasks.AllSetFieldsOf(campaign);
fieldMask.Paths.AddRange(new string[] {
    "maximize_conversions.target_cpa_micros",
});

// Creates an operation to update the campaign with the specified field.
CampaignOperation operation = new CampaignOperation()
{
    Update = campaign,
    UpdateMask = fieldMask
};

请注意，对于在 Google Ads API protocol buffers 中定义为 optional 的字段，上述“不正确”示例确实会按预期运行。但是，由于 target_cpa_micros 不是 optional 字段，因此“不正确”示例不会更新出价策略以清除 target_cpa 字段。