如何在UITableView的switch語句中創建一個變量？

Question

我在建立一個tableView，它有三個部分。 我有前兩個工作，但最後一個是有點抵抗。 我的問題似乎涉及試圖在switch語句內聲明一個變量，實際上是一個嵌套的switch語句。 從我讀過的這不是一個好主意，但在這種情況下，它似乎是唯一的選擇。

有問題的部分動態地容納與特定設備相關聯的Alert對象的數量。警報來自核心數據並取代「日期」和「警報消息」我想顯示警報中的信息。我正在使用NSFetchRequest檢索相關的警報。這將返回按照我想要的方式排序的Alert對象數組。要在使用

Alert *alert = [allAlerts objectAtIndex:indexPath.row]; 

看來我不能宣佈在switch語句中的變量該行正確的警報顯示在的cellForRowAtIndexPath我一直在試圖拉回到正確的信息。任何想法如何解決這個問題？我將不得不在doSelectRowForIndexPath中做類似的事情，因爲我需要在選中單元格時推送一個詳細視圖。

我試過在switch語句之外聲明這個變量，但這不會起作用，因爲index.row可以要求一個對象存在於Alert中並不存在的索引，並且會導致程序崩潰。

有問題的代碼是在這個方法的底部：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { 

//Cell Identifiers 
static NSString *attributeCellIdentifier = @"attributeCellIdentifier"; 
static NSString *operatingInfoCellIdentifier = @"operatingInfoCellIdentifier"; 
static NSString *alertCellIdentifier = @"alertCellIdentifier"; 

//Create Attribute Cell If Required 
UITableViewCell *attributeCell = [tableView dequeueReusableCellWithIdentifier:attributeCellIdentifier]; 
if (attributeCell == nil) { 
    attributeCell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:attributeCellIdentifier] autorelease]; 
    attributeCell.selectionStyle = UITableViewCellSelectionStyleNone; 
} 

//Create Operating Info Cell If Required 
UITableViewCell *operatingInfoCell = [tableView dequeueReusableCellWithIdentifier:operatingInfoCellIdentifier]; 
if (operatingInfoCell == nil) { 
    operatingInfoCell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:operatingInfoCellIdentifier] autorelease]; 
    operatingInfoCell.selectionStyle = UITableViewCellSelectionStyleNone; 
} 

//Create Alert Cell 

UITableViewCell *alertCell = [tableView dequeueReusableCellWithIdentifier:alertCellIdentifier]; 
if (alertCell == nil) { 
    alertCell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue2 reuseIdentifier:alertCellIdentifier] autorelease]; 
    alertCell.accessoryType = UITableViewCellAccessoryDisclosureIndicator; 
} 


switch (indexPath.section) { 
    //Attribute Section 
    case 0: 
     switch (indexPath.row) { 
      case kEquipmentAttributeSectionNameRow: 
       attributeCell.textLabel.text = @"Name"; 
       attributeCell.textLabel.textAlignment = UITextAlignmentRight; 
       attributeCell.selectionStyle = UITableViewCellSelectionStyleNone; 
       [attributeCell.contentView addSubview: self.nameField]; 
       break; 
      case kEquipmentAttributeSectionLocationRow: 
       attributeCell.textLabel.text = @"Location"; 
       attributeCell.textLabel.textAlignment = UITextAlignmentRight; 
       attributeCell.selectionStyle = UITableViewCellSelectionStyleNone; 
       [attributeCell.contentView addSubview: self.locationField]; 
       break; 
      case kEquipmentAttributeSectionControllerSNRow: 
       attributeCell.textLabel.text = @"Serial #"; 
       attributeCell.textLabel.textAlignment = UITextAlignmentRight; 
       attributeCell.selectionStyle = UITableViewCellSelectionStyleNone; 
       [attributeCell.contentView addSubview: self.controllerSNField]; 
       break; 
      case kEquipmentAttributeSectionEquipTypeRow: 
       attributeCell.textLabel.text = @"EquipType"; 
       attributeCell.textLabel.textAlignment = UITextAlignmentRight; 
       attributeCell.selectionStyle = UITableViewCellSelectionStyleNone; 
       [attributeCell.contentView addSubview: self.equipTypeField]; 
       break; 
     return attributeCell; 
     } 
     break; 
    //Operating Info Section 
    case 1: 
     //Grab First Item in Event Array 
     switch (indexPath.row) { 
      //Event *recentEvent = [allEvents objectAtIndex:0]; 

      //Last Update Row 
      case 0: 
       //Event *recentEvent = [allEvents objectAtIndex:0]; 
       operatingInfoCell.textLabel.numberOfLines = 0; 
       operatingInfoCell.textLabel.textAlignment = UITextAlignmentCenter; 
       operatingInfoCell.textLabel.text = @"Last Update"; 
       //operatingInfoCell.detailTextLabel.baselineAdjustment = UIBaselineAdjustmentAlignCenters; 
       operatingInfoCell.detailTextLabel.text = recentEvent.date; 
       return operatingInfoCell; 
       break; 
      //AvgSpeed Row 
      case 1: 
       operatingInfoCell.textLabel.numberOfLines = 0; 
       operatingInfoCell.textLabel.textAlignment = UITextAlignmentCenter; 
       operatingInfoCell.textLabel.text = @"Avg Speed"; 
       operatingInfoCell.detailTextLabel.text = recentEvent.avgSpeed;   
       return operatingInfoCell; 
       break; 
      //MaxSpeed Row 
      case 2: 
       operatingInfoCell.textLabel.numberOfLines = 0; 
       operatingInfoCell.textLabel.textAlignment = UITextAlignmentCenter; 
       operatingInfoCell.textLabel.text = @"Max Speed"; 
       operatingInfoCell.detailTextLabel.text = recentEvent.maxSpeed; 
       return operatingInfoCell; 
       break; 
      //Lifetime Row 
      case 3: 
       operatingInfoCell.textLabel.numberOfLines = 0; 
       operatingInfoCell.textLabel.textAlignment = UITextAlignmentCenter; 
       operatingInfoCell.textLabel.text = @"Lifetime"; 
       operatingInfoCell.detailTextLabel.text = recentEvent.lifetime; 
       return operatingInfoCell; 
       break; 
     } 
     break; 
    //Alert Section 

//==========================right here========================================= 

    Alert *alert = [[allAlerts objectAtIndex:indexPath.row]; 
    //[alert retain]; 
    case 2: 
     alertCell.textLabel.text = alert.date;//@"Date"; 
     alertCell.detailTextLabel.text = @"Alert Message"; 
     return alertCell; 
    //End of Outside Switch Statement 
    default: 
     break; 
    } 

    return attributeCell; //For the Compiler 
} 

Answer 1

您可以通過使用大括號這樣的聲明switch語句的情況下，內部變量：

case 2: { 
    Alert *alert = [allAlerts objectAtIndex:indexPath.row]; 

    alertCell.textLabel.text = alert.date;//@"Date"; 
    alertCell.detailTextLabel.text = @"Alert Message"; 
    return alertCell; 
} break; 

Answer 2

你可以嘗試聲明：

Alert *alert = nil; 

switch語句之前（可能在方法的開始），和只是使用作業：

alert = [allAlerts objectAtIndex:indexPath.row]; 

裏面的switch語句當行有效。