ios - objective-c - 在运行时创建一个变量名并计算它的值

Question

我有几个定义为静态变量的键:

static NSString icon_0 = @"image_0.png";
static NSString icon_1 = @"some_image_with_a_different_name.png";
static NSString icon_3 = @"picure_of_a_bear.png";

现在在我获取索引路径的数据源方法中，我想从字符串创建变量名称:

-(UICollectionviewCell*)cellForIndexPath:(NSIndexPath *)path
{
  NSString *varName = [NSString stringWithFormat:@"icon_%d",path.row];
  // here I need the static NSString which corresponds to the var name created
 // i.e 
  NSString imageName;
 if (indexPath.row == 0)
{
  imageName = @"image_0.png";
}

// would be much nicer to do something like

NSString *imageName = [varName evaluate]; // get the content out of it...
}

How can I do this on static variable?

我试过了

NSString *iconName = [self valueForKey:str];

但它不是 iVar，所以无法正常工作...

Answer 1

我不会使用静态变量，而是像这样使用静态字典:

可运行的例子:

#import <Foundation/Foundation.h>

NSDictionary *DDImageName(NSString *varName);
NSDictionary *DDImageName(NSString *varName) {
    static NSDictionary *dict = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        //TODO
        //add all names and the image names here
        dict = @{@"icon_0": @"image_0.png",
                    @"icon_1": @"some_image_with_a_different_name.png",
                    @"icon_2": @"picure_of_a_bear.png"};
    });

    return dict[varName];
}

//demo only
int main(int argc, char *argv[]) {
    @autoreleasepool {
        NSString *varName = @"icon_0";
        NSString *imgName = DDImageName(varName);
        NSLog(@"imageName for %@ = %@", varName, imgName);      
    }
}