如何将选择器视图中选择的行从应用程序委托链接到视图控制器中的变量？

Question

我对 UIPickerView 有疑问。我在应用程序委托中运行此方法：

- (id) init {
    if([super init] == nil) return nil;
    myGoal = [[NSArray alloc] initWithObjects:
              @"Select Goal",@"First Class Honors",@"Second Class, Upper",@"Second Class, Lower", @"Third Class Honors", @"Pass with Merit, Bachelor",@"Pass, Bachelor", nil];
    return self;
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row
       inComponent:(NSInteger)component {

    NSLog(@"picked row: %i, component: %i", row, component);
    NSLog(@"the value: %@", [self.myGoal objectAtIndex:row]);

在 viewcontroller.m 文件中，我链接了一个 IBAction 来在按下时进行计算。但为了进行计算，我需要能够知道在应用程序委托的方法中选择了哪一行。

在我的 IBAction 中：

- (IBAction) calculateGoal: (id) sender {

    **//--i want to link the selected pickerview row to a fix integer in his case the GPA. how sould i do this?** 
    if (row == 1) {
        double selectedGPA = 4.5;
    }
    if (row == 2) {
        double selectedGPA = 4.0;
    }
    if (row == 3) {
        double selectedGPA = 3.5;
    }
    if (row == 4) {
        double selectedGPA = 3.0;
    }
    if (row == 5) {
        double selectedGPA = 2.5;
    }
    if (row == 6) {
        double selectedGPA = 2.0;
    }

    //--change text to numbers
    double gpa = [txtGPA.text doubleValue];
    double totalau = [txtTotalAU.text doubleValue];
    double remainingau = [txtRemainingAU.text doubleValue];
    double x = gpa * totalau;
    double gpagoal = (selectedGPA * (totalau + remainingau) - x)/remainingau; //should replace 3.5 with a variable(selectedGPA) related with goal. First Class = 4.5 Second Class Upper = 4.0, Second Class Lower = 3.5, Third Class = 3.0, Pass with Merit = 2.5, Pass =2.0

问题： 1.在我的视图controller.m的IBAction中，我希望能够拉出当前选择的选择器（app delegate.m文件中的方法）的哪一行，以便我可以将相应的值分配给变量“selectedGPA”。

2.应用程序委托的 IBAction 方法中的 if 语句是否正确过滤掉所选行并将整数分配给变量“selectedGPA”？

Answer 1

使用委托。将 AppDelegate 设置为 UIPickerView 的委托。

self.picker.delegate = [[UIApplication sharedApplication] delegate];

Answer 2

我设法解决了我的问题。我不确定这是否是正确的方法，或者我很幸运它有效。

int row;
double selectedGPA;

row = [myPicker selectedRowInComponent:0];

//--i want to link the selected pickerview row to a fix integer in his case the GPA. how sould i do this.
if(row == 0){
    selectedGPA = 0;
}
else if (row == 1) {
    selectedGPA = 4.5;
}
else if (row == 2) {
    selectedGPA = 4.0;
}
else if (row == 3) {
    selectedGPA = 3.5;
}
else if (row == 4) {
    selectedGPA = 3.0;
}
else if (row == 5) {
    selectedGPA = 2.5;
}
else
    selectedGPA = 2.0;