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Question

我正在为设计游戏的女儿做一个简单的程序。我只想让Mac拿出一个从1到6的随机数，并将其与用户的猜测进行比较，然后获得用于确定玩家在棋盘游戏中可以移动多少空间的差异。一切正常，除了程序生成的差异总是3.它正确生成随机数并正确读取用户的输入。这是代码。我真的很感激帮助。我是新手，意识到可能有一个非常简单的答案。我已经搜索和搜索，并没有拿出一个解决方案。有一点它正确地产生了差异，但现在不是。非常感谢！

// 
// AstroGuessAppDelegate.h 
// 
// Created by Trent Evans on 3/7/11. 
// Copyright 2011 __MyCompanyName__. All rights reserved. 
// 

#import <Cocoa/Cocoa.h> 

int macPick; 
int numberGuess; 
int numberDiff; 

@interface AstroGuessAppDelegate : NSObject { 
    IBOutlet NSWindow *window; 
    IBOutlet id moveResultLabel; 
    IBOutlet id thinkingLabel; 
    IBOutlet NSComboBox *numberGuessBox; 
} 
- (IBAction)compareNumbersAndSendResults:(id)sender; 
- (IBAction)macThinkOfNumber:(id)sender; 
@end 



// 
// AstroGuessAppDelegate.m 
// 
// Created by Trent Evans on 3/7/11. 
// Copyright 2011 __MyCompanyName__. All rights reserved. 
// 

#import "AstroGuessAppDelegate.h" 

@implementation AstroGuessAppDelegate 


- (IBAction)macThinkOfNumber:(id)sender { 

    macPick = (arc4random() % 6) + 1; 
    NSString *thinkingLabelText = [NSString stringWithFormat: @"Ok. I'm thinking of a number."]; 
    [thinkingLabel setStringValue:thinkingLabelText]; 

} 

- (IBAction)compareNumbersAndSendResults:(id)sender { 

    numberGuess = [numberGuessBox intValue]; 
    numberDiff = macPick - numberGuess; 
    if (numberDiff<0) { 
     numberDiff = numberDiff * -1; 
    } 
    NSString *moveResultLabelText; 
    if (numberDiff=0) { 
     moveResultLabelText = [NSString stringWithFormat:@"My number was %i. Your number was %i. The difference is %i. \nBLAST OFF!\nMove forward 6 spaces", macPick, numberGuess, numberDiff]; 
    } 
    if (numberDiff=1) { 
     moveResultLabelText = [NSString stringWithFormat:@"My number was %i. Your number was %i. The difference is %i. \nORBIT!\nMove forward 4 spaces", macPick, numberGuess, numberDiff]; 

    } 
    if (numberDiff=2) { 
     moveResultLabelText = [NSString stringWithFormat:@"My number was %i. Your number was %i. The difference is %i. \nRE-ENTRY!\nMove forward 2 spaces", macPick, numberGuess, numberDiff]; 

    } 
    if (numberDiff=3) { 
     moveResultLabelText = [NSString stringWithFormat:@"My number was %i. Your number was %i. The difference is %i. \nSPLASHDOWN!\nMove forward 1 space", macPick, numberGuess, numberDiff]; 

    } 
    else { 
     moveResultLabelText = [NSString stringWithFormat:@"My number was %i. Your number was %i. The difference is %i. \nBLACK HOLE!\nSorry. You don't get to move.", macPick, numberGuess, numberDiff]; 

    } 


    [moveResultLabel setStringValue:moveResultLabelText]; 

} 


@end 

Answer 1

嘿，我花了一分钟才弄清楚发生了什么事。

简单地说，有之间的差异：

if (numberDiff=1) { 

而且

if (numberDiff==1) { 

第一个是做一个分配。它将采用值1，将其分配到numberDiff，并使用新值numberDiff作为if语句的条件。由于1是一个真正的价值，这将成功。

第二个是做比较。它将采用值1并将其与numberDiff的值进行比较。如果这两个值相等，那么总体说明将产生一个真值。

所以基本上，你需要使用==而不是=。

您总是看到“3”情况的结果，因为这是最后一条if语句。该程序能够将3分配到numberDiff，因此它将使用该案例中的文本更新NSTextField。

Answer 2

在你if语句必须赋值运算符=，而不是比较操作==，所以每if是真实的，执行的最后一个是一个3。

你会更好使用这个switch：

switch(numberDiff) 
{ case 0: 
     moveResultLabelText = [NSString stringWithFormat:@"My number was %i. Your number was %i. The difference is %i. \nBLAST OFF!\nMove forward 6 spaces", macPick, numberGuess, numberDiff]; 
     break; 
    case 1: 
     etc. 
    default: 
     moveResultLabelText = [NSString stringWithFormat:@"My number was %i. Your number was %i. The difference is %i. \nBLACK HOLE!\nSorry. You don't get to move.", macPick, numberGuess, numberDiff]; 
} 

接下来，您必须声明所有的变量为全局文件的顶部：

int macPick; 
int numberGuess; 
int numberDiff; 

如果这些不同的共享方法，那么它们应该是实例变量，在这种情况下，macPick是一个实例变量。这应该在@interface声明：

@interface AstroGuessAppDelegate : NSObject 
{ 
    int macPick; 
    etc. 

它看起来像另外两个只用于compareNumbersAndSendResults如此宣布他们有：

- (IBAction)compareNumbersAndSendResults:(id)sender 
{ 
    int numberGuess; 
    int numberDiff; 
    etc. 

在一个小的变化为：

numberDiff = numberDiff * -1; 

到

numberDiff = -numberDiff; 

甚至使用ABS功能：

numberDiff = abs(macPick - numberGuess);