文件的路徑由另一個視圖控制器修改

Question

我有2個將請求發送到Web服務的視圖控制器。 接收到數據后，數據將保存到“文檔”文件夾中的文件中。

這些是2個VC：

Live_VC：

#import "FV_Live_ViewController.h"

@interface FV_Live_ViewController ()
@end

@implementation FV_Live_ViewController

NSArray  *paths;
NSString *documentsDirectory;
NSString *path;

- (void)viewDidLoad {

paths              = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
documentsDirectory = [paths firstObject];

[self sendRequest];    // first request of data ("Live" data)
}

- (void)sendRequest {
// other code

// request of "Live" data
[urlRequest startWithCompletion:^(URLRequest *request, NSData *data, NSError *error, BOOL success) {
    if (success) {
        // other code

        NSString *filename = [NSString stringWithFormat:@"months.plist"];   
        path = [documentsDirectory stringByAppendingPathComponent:filename];    // path = "...\months.plist"

        // second request of data (monthly data) if months.plist doesn't exists
        if (![[NSFileManager defaultManager] fileExistsAtPath: path]) {
            [self sendMonthRequest];
        }
    }
}];
}    

- (void)sendMonthRequest {

[urlRequest startWithCompletion:^(URLRequest *request, NSData *data, NSError *error, BOOL success) {            
    if (success) {
        // other code

        [monthlyArray writeToFile: path atomically:YES];    // path should be "...\months.plist" while it is "...\yesterday.plist"
    }
}];
}

@end

Today_VC：

#import "FV_Today_ViewController.h"

@interface FV_Today_ViewController ()
@end

@implementation FV_Today_ViewController

NSArray  *paths;
NSString *documentsDirectory;
NSString *path;

- (void)viewDidLoad {

paths              = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
documentsDirectory = [paths firstObject];

[self sendRequest];        // first call of "sendRequest" to get today data
}

- (void)sendRequest {
//  other code

// request of "Today" data
[urlRequest startWithCompletion:^(URLRequest *request, NSData *data, NSError *error, BOOL success) {
    if (success) {       
        //  other code

        NSString *filename = [NSString stringWithFormat:@"today.plist"];
        path = [documentsDirectory stringByAppendingPathComponent:filename];    // path = "...\today.plist"

        [dataDictionary writeToFile: path atomically:YES];      // save data to today.plist

        // second call of "sendRequest" to get yesterday data only if yesterday.plist doesn't already exists)           
        filename = [NSString stringWithFormat:@"yesterday.plist"];
        path = [documentsDirectory stringByAppendingPathComponent:filename];    // path = "...\yesterday.plist"
        if (![[NSFileManager defaultManager] fileExistsAtPath:path])
            [self sendRequest];
    }
}];
}

@end

在每個VC中，我都使用NSString（“路徑”）存儲路徑，但是問題在於，在“ sendMonthRequest”方法（Live_VC）中，路徑的值是在另一個VC（Today_VC）中設置的值。 怎么可能呢？ 第二個VC如何更改第一個VC中的NSString的值？

謝謝，Corrado

Answer 1

之所以得到此結果，是因為您將“路徑”設置為文件頂部，從而使其成為全局變量。 用花括號將其包圍，然后它將是一個普通的ivar，

@implementation FV_Today_ViewController {

NSArray  *paths;
NSString *documentsDirectory;
NSString *path;
}