objective-c - Objective-C 前向方法声明

Question

我已经formatSearchString为一个类编写了一个方法，并试图在它实现之前在线调用它（没关系？）。我收到此错误：

Error: Semantic Issue
Use of undeclared identifier 'formatSearchString'

我正在使用 XCode 4.6.2

接口文件FHViewController.h：

#import <Foundation/Foundation.h>

@interface FHViewController : UITableViewController
<UITableViewDataSource, UITableViewDelegate, NSURLConnectionDataDelegate>
@property(strong, nonatomic) NSString *searchTerm;
- (NSString *)formatSearchString:(NSString *)userEntry;
@end

实施文件FHViewController.m：

#import "FHViewController.h"

@interface FHViewController()
- (NSString *)formatSearchString:(NSString *)userEntry;
@end

@implementation FHViewController
@synthesize searchTerm;

-(void)viewDidLoad
{
     [super viewDidLoad];
     NSString *formatted = [formatSearchString userEntry:searchTerm];
}

- (NSString *)formatSearchString:(NSString *)userEntry
{
     NSLog(@"User Entry: %@", userEntry);
     return @"Dummy string for now";
}
@end

Answer 1

NSString *formatted = [formatSearchString userEntry:searchTerm];

那条线是错误的。注意区别：

NSString *formatted = [self formatSearchString:searchTerm];

Answer 2

您正在使用 formatSearchString 作为变量名，而不是方法名，您需要在对象上调用 formatSearchString：

NSString *formattedString = [self formatSearchString:mySearchString];

Answer 3

Objective C 中方法调用的语法是[receiver method: param1 ...]. 因此，您需要将代码更改为：

-(void)viewDidLoad
{
    [super viewDidLoad];
    NSString *formatted = [self formatSearchString: searchTerm];
}