Question

我收到以下错误：

"warning: conflicting types for '-(Fraction *) add: (Fraction *) f;"

行：

-(Fraction *) add: (Fraction *) f;

这是我的标题代码：

  // Define the Fraction class

    @interface Fraction : NSObject {
        int numerator;
        int denominator;
    }
    @property int numerator, denominator;

    -(void) print;
    -(void) setTo: (int) n over: (int) d;
    -(double) convertToNum;
    -(void) add: (Fraction *) f;
    -(void) reduce;

    @end

Here is my .m code:
#import "Fraction.h"

@implementation Fraction
@synthesize numerator, denominator;
-(void) print
{
    NSLog (@"%i / %i", numerator, denominator);
}
-(double) convertToNum
{
    if (denominator != 0)
        return (double) numerator / denominator;
    else
        return 1.0;
}
-(void) setTo: (int) n over: (int) d
{
    numerator = n;
    denominator = d;
}


-(void) reduce 
{
    int u = numerator;
    int v = denominator;

    int temp;

    while (v != 0) {
        temp = u % v;
        u = v;
        v = temp;
    }

    numerator /= u;
    denominator /= u;

}

-(Fraction *) add: (Fraction *) f;
{
    // To add two fractions:
    // a/b + c/d = ((a*d) + (b*c)) / (b *d)
    // multiply the denominators
    // then mulitply each numerator by the OPPOSITE
    // denominator

    // result will store the result of the addition
    Fraction *result = [[Fraction alloc] init];
    int     resultNum, resultDenom;

    resultNum = numerator * f.denominator + denominator * f.numerator;
    resultDenom = denominator * f.denominator;

    [result setTo: resultNum over: resultDenom];
    NSLog(@"%i, %i", resultNum, resultDenom);
    [result reduce]; // reduces the numerator and denominator
    // as both are instance (classwide) variables
    NSLog(@"%i is the result", result);
    return result;
}
@end

Answer 1

你有两种不同的add实现：一个是：

-(void) add: (Fraction *) f;

界面内的

（.h文件）。另一个是在实现（.m文件）

中

-(Fraction *) add: (Fraction *) f;

您需要更改标题以读取后一个声明，以便它返回一个Fraction指针，而不是void。

Answer 2

那是因为在你的头文件中，你已经将返回类型声明为void：

-(void) add: (Fraction *) f;

然而，在您的实现中，您实现了返回Fraction指针的方法：

-(Fraction *) add: (Fraction *)

此外，您的实现中有分号，可能只是复制粘贴错误？

Answer 3

您声明add方法在您的界面中返回void，但您的实现返回Fraction *

如何返回类的实例？

3 个答案: