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how can I limit property when type casting (typescript)

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0

How can I get expected result and what's the best approach to limit property when type casting ??

interface user 
 name: string
 password: string


interface userEntity 
 name: string


const user: user = 
 name: 'name',
 password: 'password'


const result = user as userEntity;
// output name: 'name', password: 'password' 
// expected name: 'name' 

typescript type-conversion

share|improve this question

asked Mar 24 at 17:15

Tung TseTung Tse

3014

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What the real case here? Force casting is not good practice. And even if it was ok, what is the difference between the "user entity" and the "user"? Please give a more real-life scenario
  
  – MCMatan
  Mar 24 at 17:24
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  the user is a model get from database ORM, then I wanna response to frontend exclude password. Actually, I can new a variable exclude password for the response, but I don't think it is a good approach.
  
  – Tung Tse
  Mar 24 at 18:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It sounds like a better approach to me. As a rule of thumb, any time you are force casting, you probably are doing something wrong. You can have a dedicated constructor that accepts User input
  
  – MCMatan
  Mar 24 at 18:54
  

  
  
  
  

add a comment | 

0

How can I get expected result and what's the best approach to limit property when type casting ??

interface user 
 name: string
 password: string


interface userEntity 
 name: string


const user: user = 
 name: 'name',
 password: 'password'


const result = user as userEntity;
// output name: 'name', password: 'password' 
// expected name: 'name' 

typescript type-conversion

share|improve this question

asked Mar 24 at 17:15

Tung TseTung Tse

3014

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What the real case here? Force casting is not good practice. And even if it was ok, what is the difference between the "user entity" and the "user"? Please give a more real-life scenario
  
  – MCMatan
  Mar 24 at 17:24
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  the user is a model get from database ORM, then I wanna response to frontend exclude password. Actually, I can new a variable exclude password for the response, but I don't think it is a good approach.
  
  – Tung Tse
  Mar 24 at 18:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It sounds like a better approach to me. As a rule of thumb, any time you are force casting, you probably are doing something wrong. You can have a dedicated constructor that accepts User input
  
  – MCMatan
  Mar 24 at 18:54
  

  
  
  
  

add a comment | 

How can I get expected result and what's the best approach to limit property when type casting ??

interface user 
 name: string
 password: string


interface userEntity 
 name: string


const user: user = 
 name: 'name',
 password: 'password'


const result = user as userEntity;
// output name: 'name', password: 'password' 
// expected name: 'name' 

typescript type-conversion

share|improve this question

asked Mar 24 at 17:15

Tung TseTung Tse

3014

interface user 
 name: string
 password: string


interface userEntity 
 name: string


const user: user = 
 name: 'name',
 password: 'password'


const result = user as userEntity;
// output name: 'name', password: 'password' 
// expected name: 'name' 

share|improve this question

asked Mar 24 at 17:15

Tung TseTung Tse

3014

share|improve this question

asked Mar 24 at 17:15

Tung TseTung Tse

3014

asked Mar 24 at 17:15

Tung TseTung Tse

3014

asked Mar 24 at 17:15

Tung TseTung Tse

3014

1 Answer
1

active

oldest

votes

1

Type casting has no effect at runtime, the values in object will remain the same. Type casting only purpose is to suppress compilation errors when type-checking, when you know better than the compiler what the actual type of the object should be.

To copy only a subset of properties when assigning a value to another object, you have to do it explicitly at runtime. There is a multitude of possible ways to do that, for example

const result: userEntity = name: user.name;

share|improve this answer

answered Mar 24 at 19:33

artemartem

16.9k33345

add a comment | 

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1

Type casting has no effect at runtime, the values in object will remain the same. Type casting only purpose is to suppress compilation errors when type-checking, when you know better than the compiler what the actual type of the object should be.

To copy only a subset of properties when assigning a value to another object, you have to do it explicitly at runtime. There is a multitude of possible ways to do that, for example

const result: userEntity = name: user.name;

share|improve this answer

answered Mar 24 at 19:33

artemartem

16.9k33345

add a comment | 

1

Type casting has no effect at runtime, the values in object will remain the same. Type casting only purpose is to suppress compilation errors when type-checking, when you know better than the compiler what the actual type of the object should be.

To copy only a subset of properties when assigning a value to another object, you have to do it explicitly at runtime. There is a multitude of possible ways to do that, for example

const result: userEntity = name: user.name;

share|improve this answer

answered Mar 24 at 19:33

artemartem

16.9k33345

add a comment | 

Type casting has no effect at runtime, the values in object will remain the same. Type casting only purpose is to suppress compilation errors when type-checking, when you know better than the compiler what the actual type of the object should be.

To copy only a subset of properties when assigning a value to another object, you have to do it explicitly at runtime. There is a multitude of possible ways to do that, for example

const result: userEntity = name: user.name;

share|improve this answer

answered Mar 24 at 19:33

artemartem

16.9k33345

const result: userEntity = name: user.name;

share|improve this answer

answered Mar 24 at 19:33

artemartem

16.9k33345

answered Mar 24 at 19:33

artemartem

16.9k33345

answered Mar 24 at 19:33

artemartem

16.9k33345